Former UN secretary-general Kofi Annan has marked the Queen's 90th year by praising her "steadfast devotion" to the Commonwealth.
Speaking at the Commonwealth Day service held at Westminster Abbey he paid tribute to the monarch who, in her annual address to the family of nations, called on the Commonwealth's citizens to support those in need.
Mr Annan said the Commonwealth not only strengthened links between member countries, it offered practical support from election monitoring to promoting security co-operation.
He added: "Today the Commonwealth stands as a confident, modern, multi-cultural and proudly inclusive organisation."
The former UN secretary-general went on to say about the Queen's involvement with the institution she heads, that nobody "has made a greater contribution to its achievements than Your Majesty.
"You have shown an unwavering and steadfast devotion to this grand project. We are greatly honoured and deeply grateful for your extraordinary commitment."
The Westminster Abbey service was the largest annual inter-faith gathering in the UK and hymns were sang, and prayers read in honour of the Commonwealth.
Among the guests were David Cameron, former prime minister John Major, the Duke of Edinburgh, the Duke and Duchess of Cambridge, Prince Harry and a host of dignitaries.