Early life, family and education
Sinclair's father and grandfather were engineers; both had been apprentices at Vickers the shipbuilders. His grandfather George Sinclair was an innovative naval architect who got the paravane, a mine sweeping device, to work. George Sinclair's son, George William "Bill" Sinclair, wanted to take religious orders or become a journalist. His father suggested he train as an engineer first; Bill became a mechanical engineer and remained in the field. At the outbreak of World War II in 1939 he was running his own machine tools business in London, and later worked for the Ministry of Supply.
Clive Sinclair was born to George Sinclair and Thora Edith Ella Marles in 1940 near Richmond, then in Surrey. He and his mother left London for safety to stay with an aunt in Devon, where they eventually travelled to Teignmouth. A telegram arrived shortly afterwards, bringing the news that their home in Richmond had been bombed. Sinclair's father found a house in Bracknell in Berkshire. His brother Iain was born in 1943 and his sister Fiona in 1947.
At the age of 14, Sinclair designed a submarine. During holidays he could pursue his ideas and teach himself what he wanted to know. Sinclair had little interest in sports and found himself out of place at school. He preferred the company of adults, which he got only from his family.
Sinclair attended Boxgrove Preparatory School, excelling in mathematics. By the time he was ten, his father had financial problems. He had branched out from machine tools and planned to import miniature tractors from the U.S.; he had to give up the business. Because of his father's problems, Sinclair had to move school several times. After a time at Reading School, Sinclair took his O-levels at Highgate School in London in 1955 and A-levels in physics, pure maths, and applied maths at St. George's College, Weybridge.
During his early years, Sinclair earned money mowing lawns and washing up, and earned 6d (old pence) more than permanent staff in a café. Later he went for holiday jobs at electronic companies. At Solatron he inquired about the possibility of electrically propelled personal vehicles. Sinclair applied for a holiday job at Mullard and took one of his circuit designs; he was rejected for precociousness. While still at school he wrote his first article for Practical Wireless.
Sinclair did not want to go to university when he left school at the age of 18 and instead he sold miniature electronic kits by mail order to the hobby market.