'The Queen's leadership is special When you put 54 leaders together in that room, they are sitting around as though they are in a large family drawing room. They are relaxed. It's all done with great humour," he says. That's why, for the smaller countries, it's so important to feel they belong to something worthwhile. It is truly global. His book contains scores of examples in which the Commonwealth has worked quietly to confront dictators, safeguard freedom or improve daily life for people. He cites his repeated conversations with presidents Musharraf of Pakistan and Mugabe of Zimbabwe, or his pride in changes to the primary school curriculum in Ghana: "A couple of years later, you see kids with just that bit more confidence coming through as a result." Many countries would regard this kind of privileged membership of a group that embraces one quarter of the countries in the world as priceless. But McKinnon makes it clear that the FCO places negligible importance on the Commonwealth. He gives a series of examples. On one occasion, six members of the Commonwealth Ministerial Action Group (CMAG) - all foreign ministers - flew to London to discuss a political crisis. The FCO couldn't be bothered to send a minister to walk across St James's Park to see them. "If George Bush came to town," says Sir Don, "all the foreign ministers would have been there." On another occasion CMAG was in New York in a crisis session when Peter Hain, then an FCO minister, quit the room, saying that he had another meeting to go to. It was only the following day that I found out he'd gone off to address some political spouses! In his book he reveals how he confronted Sir Michael (now Lord) Jay, the notoriously careerist and Blair-friendly FCO permanent secretary: "I told him bluntly that he had to demonstrate a firmer commitment to UK ministerial attendance at these meetings. I reminded him that the FCO had a secretary of state and three ministers in Whitehall. Finally, McKinnon warned the hapless Jay that his "commitment and reputation needed sharpening up." "In all my discussions with Sir Michael Jay," writes Sir Don, "I never had the feeling he was a committed Commonwealth man." In general, says Sir Don, "the Foreign Office has left the Commonwealth to one side of the mainstream of activity. You could say - well, that's to be expected. After all, for every £1 they give the Commonwealth they give £350 to the EU, £50 to the UN and £10 to Nato. Though he stresses that these figures are from 2008. Matters may have improved since the 2010 election, though. "William Hague has certainly put a lot more effort into the Commonwealth," acknowledges Sir Don, adding, "David Cameron has talked about it a few times." He is full of praise for Lord Howell, appointed a foreign office minister in 2010: "I was really pleased when he became a minister, because I thought, there's someone there who actually knows what's going on." I am obliged to break it to him that Lord Howell was sacked in last year's reshuffle (in a phone call from his son-in-law, the Chancellor). Sir Don looks surprised and a bit crestfallen. I ask him what it means to have the Queen as head of the Commonwealth. "It does give the Commonwealth something that no other international organisation has," he replies. She gets a tremendous amount of affection from Commonwealth leaders. They truly all do like her very much. They enjoy meeting her. They enjoy chatting with her. She keeps people at ease. They all regard it as something very special. He also praises the role of the Prince of Wales: "We recently had Charles and Camilla in New Zealand, and I'd be prepared to say that the heir to the throne is far more relaxed than I have ever seen him. The result of that is that he gets along famously with any contact he has. His tour of NZ and, I'm told, Australia was very, very successful. Mention of the Prince of Wales brings us to one of the most vexed questions in the Commonwealth, though rarely discussed openly: who will take over when the Queen steps down? In his book, Sir Don carefully sets out the situation: "It is not an inherited role, so, while the Prince of Wales would automatically become king, there would have to be a process for managing a transition to head of the Commonwealth. If it happened on my watch, the process would be along these lines: I would see if there was a consensus among Commonwealth leaders in favour of the Prince of Wales. If this was quickly apparent, an announcement could be made before the Queen's funeral and it could subsequently be included in the new sovereign's titles. If there was no consensus, the issue could be held over until the next Commonwealth heads of government meeting. I ask him how the debate about the Queen's successor as head of the Commonwealth is going. "When I talk to leaders quite candidly on the subject, always on a one-to-one basis, no one taking records, they have all tended to follow the same line," replies Sir Don, explaining that reaching beyond the British monarchy would raise questions of "How long would their term be, and if that term finishes at a certain time what would you do then? Would you have to do it region by region? In his book he says: "In all my meetings with many Commonwealth heads of government about who will take over... there has always been a circuitous discussion that canvasses all the alternatives and eventually goes the full circle and returns to the British monarch." Before our interview ends, Sir Don quotes former President Obasanjo of Nigeria, who told him: "We don't feel diminished by having our former colonial ruler as our current head of state." Sir Don concludes: "To me that was very telling." In the Ring: A Commonwealth Memoir" by Don McKinnon (Elliott & Thompson) is available to order from Telegraph Books at £18 + £1.35 p&p. Call 0844 871 1514 or visit books.telegraph.co.uk