But then came the last Conservative Party manifesto and the innocuous-sounding Housing and Urban Development Bill. Suddenly, the accord started to fade.
First, the owner of 300 acres of Mayfair and Belgravia worth an estimated pounds 3.5bn is believed to have asked for some of his money back. Then on 3 February, it was revealed yesterday, he resigned as Conservative Party Association president in Chester, a post he had held for 16 years, withdrawing membership at the same time. A long family association - his father was a Tory MP and had preceded him as Chester president - was at an end.
What is the explanation? Yesterday, he partly blamed government policies, saying he could not 'morally stay within a party which I fundamentally believe has ideologically gone off the rails'. The real reason, however, as he said in his letter to his association chairwoman, Jill Everett, was legislation going through the Lords.
The Housing and Urban Development Bill seeks to give flat-owners with leaseholds the legal right to buy their property freeholds, a move which will cost the Duke dear. He said yesterday it was 'distressing from a personal point of view to have heritage over 300 years taken away'.
Whether the Duke, believed to be Britain's richest man, was thinking of heritage or money when he went to the House of Lords for the Bill's Second Reading on Tuesday is unclear. But, preoccupied with something, he took his seat without first swearing the oath of allegiance, which is necessary once in each Parliament. He could be fined pounds 500.
He had to be ushered from his seat to a non-member area of the chamber.