After leaving Eton, Dave spent three months in Florence before joining Christie's in 1969. At nineteen he was the youngest member of a technical department. In 1975 he joined Phillips where he was number two in the picture department. He was for ten years a consultant to the Old Master Department at Bonhams, whilst working with Johnny van Haeften, the specialist dealer in Dutch and Flemish paintings, which he did for over twenty years.
He served for many years on the vetting committee of Olympia Fine Art and Antiques Fair, was chairman of the picture vetting committee of the Grosvenor House Art and Antiques Fair, chairman of the Friends of the Reading Museum and Art Gallery for twenty years and is currently an external advisor to the Collections Committee of Eton College, and a trustee of the Reading Foundation for Art. Although he is an Old Master generalist, he has a passion for British landscape painting, with a specialist knowledge of Wilson, Constable and Danby.