Julius Neave was a leading figure in the postwar reinsurance business. He joined a small family company called Mercantile & General in 1938 and, after serving with distinction in the Second World War, returned to it in 1946. Between then and 1982, when Neave retired as managing director, M&G’s income grew 30 times over.

Julius Arthur Sheffield Neave was born in July 1919. He attended Sherborne School, but instead of going to university joined a firm run by Sir Richard Guinness, a scion of a famous family of bankers.

After barely a year’s apprenticeship in the City of London, Neave joined the 13th/18th Royal Hussars. He spent most of the war as an adjutant, serving four different commanding officers and earning plaudits from contemporaries for being “exceptionally good at keeping the show on the road”. He rose to the rank of major and was mentioned in dispatches in 1945.

Although army rules forbade servicemen from keeping diaries, Neave was among the many who disregarded the instruction, and 50 years after writing privately about the Normandy campaign he published his account of his experiences. Conscious that diaries were forbidden because of the risk that strategically important information might fall into enemy hands, the diaries are of little military moment. Nonetheless, they provide some interesting insights into soldiering. The entry for July 17, 1944, reads: “My birthday! And a very hectic day indeed . . . up all night moving, and an absolutely bloody and pestiferous journey in a thick wet mist and also dust, which all agree is comparable to the desert.” He continued: “We are undoubtedly on the eve of a battle much bigger than Alamein . . . There isn’t an orchard or field empty and if it is postponed life will be intolerable, as the place will be nothing less than a muck heap.”

Mercantile & General — a company entirely unrelated to the better known M&G unit trust and investment management house — was founded in Glasgow in 1907 to provide insurance to employers who were obliged to provide sick pay to workers who fell ill or had had accidents. It took to reinsurance — an important but largely invisible industry that insures insurers and thereby spreads the financial risks posed by potential claims — after the First World War. Openings came because until then most reinsurers were German and had been wiped out by the political, military and commercial upheavals that came with the 1914-1918 conflict.

M&G grew through the 1920s and 1930s, helped by the fact that it steered clear of marine risks that undermined the financial strength of many rivals. Neave’s task after the Second World War, however, was to build the firm’s marine reinsurance activities. He became the assistant general manager in 1964 and took overall control in 1966.

Early into his leadership he tackled a thorny question regarding the ownership of the firm he headed. Back in 1919 Sir Richard Guinness secured financial support from Swiss Re, which, thanks to its nationality, had survived the First World War and now has its London headquarters in the Gherkin. Swiss Re spent the succeeding half century as a supportive partner happy to allow M&G operational autonomy. But by 1968 M&G had grown large enough to pose conflicts of interest. Neave persuaded the Prudential to replace the Swiss.

In 1972 the Pru bought the other M&G shares owned by the Guinness family and in 1982, after retiring from M&G, Neave was appointed a non-executive director on the main board of Prudential with the commendation: “after 44 years’ service \ he has become a leading figure in the international reinsurance industry.”

Neave held a number of senior positions in representative bodies, including the Insurance Institute of London and the Chartered Insurance Institute. He also spoke widely about reinsurance at conferences, and a collection of his speeches was published in 1980.

M&G’s premium income was about £300,000 per year in 1947. It rose to £1 billion by the time Neave retired in 1982. By December 1996 Prudential had tired of the responsibility of looking after the firm Neave built and sold it back to Swiss Re for £1.75 billion.

Neave, a first cousin of Airey Neave, the Conservative Party Northern Ireland spokesman killed by the IRA in 1979, is survived by his wife, Helen, and their three daughters.

Julius Neave, CBE, general manager of the Mercantile & General Reinsurance Company, was born on July 17, 1919. He died on October 30, 2008, aged 89