Living near Richmond in Surrey as a child he enjoyed a comfortable middle class existence at home, but being precocious and being the eldest child, related better to adults than to other children. The Sinclair parents eschewed conventional, polite social reserve preferring direct, confrontational exchanges and set this pattern for their children. This unusually honest communication perhaps intensified the sense of isolation that Clive sometimes felt as a child in the company of other children.

He certainly enjoyed home much more than school life. In the summer holidays he had the benefit of his family's inventiveness to stimulate him: both grandfather and father were engineers. He began designing at an extremely early age and from the beginning understood the concept of making something real from an idea. His talented, enquiring mind led him to explore and educate himself on his own initiative. This drive, together with his sensitivity, advanced understanding and lack of interest in team sport meant that the gap between him and his peers tended to widen rather than decrease at school. This he found generally stultifying even though he found aspects to enjoy at Boxgrove Preparatory School. At aged ten the school found it could teach Clive no further in Maths and it was time to move on to secondary level education.

Unfortunately, also at this time, the family's machine tooling business went bankrupt and Bill Sinclair had to start again from nothing. The business built up again quickly, but Clive's secondary education was fragmented as a result. He went to Highgate briefly, for two or three terms, had a year at Reading - a minor public school that his father had attended before him - then moved to Dorking Grammar. He finally took A- and S-levels in physics, pure and applied maths at St. George's College, a public school in Weybridge, Surrey.

The academic school education, however, was irrelevant in terms of the acquisition of Clive's engineering skills. He independently invented the binary system while working on a proto-calculator and was disappointed to discover that it had already been invented. His attitude to learning is accepted as perfectly natural nowadays in a Montessori environment: he followed his interests with single-minded determination and ignored those that did not seem appropriate for him. The approach, however, must have exasperated his post-war conventional teachers in the English system of the time.

With his A-levels three weeks away, perhaps as a relaxation exercise, Clive spent time working out figures for manufacturing a radio circuit. His notes can be seen in an exercise book dated 19th June 1958. He also wrote an article for 'Practical Wireless', which was published. But life was not all work and Clive was renowned for his partying spirit, then as now.

For a young man who knew his own mind so clearly there was no sense in going to university. He knew he could learn everything he wanted for himself and that, for him, three years of university study would be a waste of time. Moreover, he made the decision that, as his father's business was still insecure at times the family did not need the financial drain of a son at university. When 'Practical Wireless' advertised for an editorial assistant he applied and got the job. He placated his parents by blatantly lying to them, saying that it was a holiday job, then gradually persuaded them that there were better prospects for him there than he would enjoy going via the normal university route. J F Camm, the director, was a man of strong character who dominated his tiny staff of three by force of personality. The editor unfortunately became seriously ill, the assistant editor soon collapsed under the strain and Clive found himself running the magazine single-handedly at age 17. This he found extremely easy. The work took a fraction of the week and he then had the spare time to design circuits, which were published in the magazine. They did not always work, but Clive's perspective allowed him to be philosophical enough to see the letters generated as simply more material for the magazine. He therefore made his mark and began to be noticed at an early age.

It was at an exhibition that Clive had another stroke of luck. He was fronting the 'Practical Wireless' stand when he was approached by the head of a publishing company and offered a then amazingly large salary to run it. At Bernard's Clive continued designing circuits and wrote as well as edited books. Writing took priority, as it was easier than finding people to write for him. He still worked in a staff of three, but had the title Chief Editor and earned considerably more.

Luck, however, did not go all Clive's way. In 1961 he handed in his notice to Bernard Babani and registered Sinclair Radionics Ltd as a company, having spent some time designing a pocket transistor radio and finding backing, whereupon the backer withdrew. Clive had to find work quickly, which he did with United Trade Press as a technical editor. He spent a year in this role and used it wisely to make links with manufacturers. He began to operate his company from his one room in London, but quickly moved to two rooms in Islington. The long-standing link with Cambridge came about from Clive's meeting Tim Eiloart through Mensa. He needed a base to assemble components and deal with mail order administration. Cambridge Consultants Ltd, run by Eiloart, provided this service. No sooner had the advertising appeared than the company was swamped by demand and the business began to snowball.

Clive was engaged at this time and six months after the company took off he married Ann. The marriage was to last 23 years and produce three children: Belinda, Crispin and Bartholomew. The family and business moved to Cambridge in '67 as it seemed appropriate to rationalise by moving to one base of operations.

Sinclair Radionics lasted until 1979, with various products and company spin-offs. Beginning with a mini-amplifier, the company quickly earned a name for design, quality and pioneering ideas. The overall vision was to produce in bulk and to sell cheaply. This risky but potentially profitable 'stack 'em high, sell 'em cheap' approach has made fortunes before, but carries with it the risk of bankruptcy. In the early days one strategy essential to this policy for Sinclair Radionics was production in kit form.

Miniaturisation, at which Clive proved himself so talented, was also a key idea. In 1962 Clive marketed the world's first pocket calculator, by 1976 the world's first digital wristwatch and in 1977 came the fist pocket TV.

It is sobering to remember that at the end of the 1970s computers were still commercial machines filling whole rooms and relying on tape. In Britain, only Commodore had previously launched a personal computer: at £700, a small fortune in 1978. In January 1980 Clive demonstrated the ZX80 at an exhibition in Wembley. For this product there was a choice between a cheaper kit and the ready assembled computer, which still cost less than £100.

By September more than 20,000 had been sold; Sinclair Research had had to cope with another rapid expansion and had established a base in the United States.

Manufacturing was contracted out, but efficient quality management earned the product a justified name for reliability. The bugs in the first computer's system were mostly ironed out with the follow-on product, the ZX81 again selling at less than £100. By 1982 company turnover was £30million, compared to £4.65million in the previous year. The ZX Spectrum was launched in April 1982 and changed the face of leisure in the home. Much to Clive's chagrin the Spectrum proved to be most useful for playing computer games. A whole market area developed from the computer's capacity for games.

Companies founded to invent and develop games have, in some respects driven the technology needed for this market: an aim very different from Clive's original aim with the ZX80, which was to provide a machine for the man-in-the-street interested in computer programming. The High Street has also changed to allow for this societal development. Department stores and stationers as well as electrical retailers stock computers. Dedicated games shops exist and, of course you would not be reading this now were it not for the growth of the Internet, which has depended on mass accessibility to computers.

The early 80s were a busy time for Clive. Sinclair Browne Ltd was established in 1981 and lasted until 1985 running concurrently with Sinclair Research. Patrick Browne was the main force in this project which was a publishing house dealing with translations of mainland novels and books on computing.

With a group of mostly stable and successful businesses Clive found time to develop academically. He studied for a diploma at King's College, Cambridge and was a Visiting Fellow of Robinson College, 1982-85: just over the road from his impressive house on Madingley Road, Cambridge. He was also Visiting Professor for the Department of Electronic Engineering, Imperial College of Science and Technology, London from 1984 onwards, which he defines as 'a proper job' lecturing students.

Unfortunately the Midas touch deserted Clive with the production of a new concept in personal transport: the Sinclair C5. This used a small motor powered by rechargeable batteries, but definitely not a washing machine motor as was unkindly reported at the time and set in stone by Chambers Dictionary of Biography. The C5 was far smaller and lower than the family car of the time and had three wheels. The combination proved too extreme for the British public. It received a bad press, being widely condemned as unsafe and impractical. It is interesting to note, however, that car manufacturers have since decided that the small car market is the one with most potential for growth and have worked towards Eco-friendly transport. With car pollution and gridlock threatening most major cities, the C5 might have been a prophetic solution to a problem few saw looming in the distance. If it had been four-wheeled and produced only as a concept car to guide the market… who knows? The Icarus blunder of applying the 'stack 'em high, sell 'em cheap' policy to a finished product as though for a mass market and failing enforced a period of retrenchment in Clive's business activities.

Clive famously became Chairman of British Mensa in 1980 and filled this role until 1997 when he thought it was time someone else had a go. When Clive joined the national committee it was to become involved in a Mensa which had been resurrected once, by Victor Serebriakoff, but where membership had then levelled out and begun to fall. Victor was interested in building up the society worldwide, but Mensan politics in the mother country needed more involvement and direction. There were 1700 members and people were leaving faster than they were joining. The range of activities was restricted, with little happening at national level. The next year Clive became Chairman.

This was at a time when Sinclair Research was formed to build on the success of Sinclair Radionics. Clive was already a household name and brought a certain cachet to Mensa, making it an organization people respected and wanted to join. As recognition perhaps for the effect he has had on the development of twentieth century culture he was honoured with a knighthood in 1983 and this also gave Mensa some reflected glory. His most important contribution to Mensa was something he partly funded himself: he paid for advertising in national newspapers whereas before Mensa had relied on publicity and free advertising. He also established and mostly funded the yearly conference Mensa at Cambridge, which did much to bring intellectual respectability to the society. By 1983 British Mensa had 10,000 members and 38,000 by 1996.

Clive took his Mensa duties seriously, attending a wide variety of gatherings at local, regional and national level. He made the society a household name. For all this service he never even claimed his out of pocket expenses. A strong character invariably attracts strong reaction and Clive had critics as well as ardent supporters. Criticism tended to focus on the very qualities, which enabled him to get things done. He had a disregard of petty administrative rules and his forceful determination put plans into action irrespective of opposition feelings. This meant that criticism was sometimes extremely aggressive. The bare facts of Mensa's growth, however, testify powerfully to the strength and success of his leadership.

He now lives and works in his penthouse apartment in London. He had an extra storey added to the top of the apartment block and worked to design a space, which allows him to be as creative as ever. He enjoys classical music and describes himself as 'passionate about poetry' as well as retaining his life-long love of science and mathematics. More recently he has found time to indulge a taste for poker, which he uses as a game of mathematical and social skill to exercise and hone his intelligence.