At Christie's, Van Haeften worked on integrating the stamp dealers
Robson Lowe into Christie's, He continues to collect stamps, specialising in the stamps of Malta, and has written about the
Melita issue, dual-purpose postage and revenue stamps issued by the Crown Colony of Malta from 1922 to 1926. He has also given displays to members of the Malta Study Circle on the 1925
postage due stamps of that country. He has been a member of the
Royal Philatelic Society London, since 2012. He only collects the stamps and mail of Malta, regarding its early engraved stamps as miniature works of art, and also owns a letter to
Florence Nightingale in the Crimea that was
disinfected with vinegar when it passed through Malta in order to prevent cholera being transmitted through the mail. He credits the eye for detail that he developed from collecting stamps with enabling him to appreciate the details in his chosen profession of dealing in old master Dutch paintings. In January 2017, Van Haeften closed his Duke Street gallery after 40 years in the area, after the building's owner sold it, and informed him that the Italian art dealer
Fabrizio Moretti would be moving in. Van Haeften considered taking legal action, but instead set up with reduced stock in a refurbished coach house at his home,
Beaufort House, in
Ham, near Richmond, Surrey. In 2017, he estimated that he had sold 4,800 paintings over the course of his career. ==Personal life==