In 1939 he was called up to the Royal Army Medical Corps and was captured at Dunkirk, he spent three years in a Stalag in Eastern Europe and was then released in order to escort sick prisoners of war who were being repatriated in 1943.
The De Haans noticed the large number of retired people who came to the south-east coast after the high season crowds had gone.
Seeing the potential economic value in stretching the holiday season, he persuaded the local council and other traders to find ways of welcoming the retired visitors, with special offers and discounts.
When he retired in 1984 De Haan had become an established name in travel circles, and was awarded the Officer of the Order of the British Empire, for services to tourism, in the following New Year's Honours List.
De Haan had not realised it at the time, but when he hit upon a bright idea to generate some extra revenue for his hotel, he was founding a company which, in addition to worldwide holidays and cruises, would move on to provide a plethora of insurance products, financial services, and more, all for a customer group which most advertisers ignored.