Holt was born in Hammersmith, west London, the son of a panelbeater, in 1912. He first learnt about fine wood as an apprentice cabinet-maker; and in his boatbuilding career he put his knowledge of the difference between good wood and very good wood to excellent use when it came to choosing spruce for a mast or timber for planking. But a badly broken leg, sustained in an accident while riding pillion on a motorcycle, which left him in plaster to the thigh for a long period, put an end to his cabinet-making career when he was still in his teens.
He had sailed with the Sea Scouts as a boy, helping them with their boats, and bought his first boat, a 14ft dinghy, with his brother from the writer A.P. Herbert, a close neighbour on the Thames at Hammersmith. In 1929, when he was 17, he set up business in a hut under Hammersmith Bridge where his late great-uncle John Holt had repaired boats. When building his first boat, Candlelight, he did not have enough money to buy a brass tack, let alone the metal shanks which every other builder used on their masts to hoist the sail. Jack Holt solved the problem by making a groove in the wooden mast through which the thick side of the sail was pulled up. This "boltrope" groove was laughed at at the time but is now used by all small boats.
On his first visit to Cowes in the 1930s - the time that we met - Holt competed in the championship for 14ft boats, one of which he had built. His entry was looked upon with sneers by the sailing establishment. Why should a boat-builder enter a National Championship where the elite were competing? And, to make it worse, his yard was on the River Thames at Hammersmith. Though Holt did not win he made a good placing. He was busy in the Thirties building other boats, designed for eager sailors. His boat in the 18ft class was an outstanding success as was his 12ft National.
During the Second World War Holt built lifeboats and wooden copies of enemy planes for the Government, moving with his staff down the river, taking to a former oar-making works near Putney Bridge; it is still a Jack Holt shop, selling everything you could need for a boat including clothing.
After the war, a small group from Ranelagh Sailing Club, based on the same stretch of the Thames, commissioned Holt to design a small boat. It was called a Merlin and was accepted as a fine racing boat more simply made and more economic than other 14ft boats. The first Merlin is now on show at the Maritime Museum, in Greenwich.
The Merlin was a success and in 1947 Yachting World magazine asked Holt to design a children's boat. His design could be sailed by boys and girls aged 8 to 16. They were soon sailing them very proficiently and word of this small boat went all over the world. It was called the Cadet. In those early post-war years there was still a divide in the sailing world: with the yacht club for the gentry and the sailing club for the workers. But youngsters, in Holt's cheap and simple Cadet, did not know this and when Cadets from yacht club and sailing club were out on the same bit of water the class privilege was ignored. It was the first breakthrough in solving the class problem on the water. The boat was adopted by many countries and large regattas are held for this class every year.
The Cadet was followed by a simple boat called Enterprise, commissioned for promotional purposes by the News Chronicle newspaper in 1955, with blue sails. This too became very popular and has world-wide fleets. The Asian Games, which are held every four years, between the Olympic Games, still use the Enterprise as their prime Class. Both the Cadet and the Enterprise were accepted by the International Yacht Racing Union and were recognised as International Classes. Then came an even simpler boat that people could make from kits themselves. It was called the Mirror, promoted by the Mirror newspaper titles, and it too was accepted as a World International Class. Manufactured as a kit by Bell Woodworking, it has been built in greater numbers than any other of Holt's designs; 69,744 Mirrors have been registered to date.
Other innovatory craft from Holt's design board included a single-handed boat, the Solo, and a longer one called the Hornet (1952), which was the first boat to have an aid to the crew in having a seat that extended over the water, the forerunner of what is now known as a trapeze. One of his very successful designs was the General Purpose 14 (GP14, 1950), a very wholesome boat, well adapted to sailing, going fishing, with room for a picnic, and a good boat to row.
Holt also made time too to race, both in Britain and in countries abroad. He was a first-class racing helmsman and won many championships, including three Merlin championships in that boat's early days. His boats were the first RYA Class boats to sail abroad: in Italy, Spain, France, Belgium, Sweden, the Netherlands, Switzerland, and Poland. He was invited to Australia where about five of his classes were raced and he had the joy of his life going from centre to centre in Australia, each of which held a special Jack Holt Regatta.
All these Holt boats could be built by any other builder, professional or amateur. Doing all this, Holt was a gentle man in every sense. I knew him for more than 60 years, and was his business partner for the past 50, and never heard a cross word or a refusal to help anyone.
John Lapworth Holt, boat designer: born London 18 April 1912; married Iris Thornton (one daughter, and one son deceased); died Chichester 14 November 1995.