Liz Windsor at 90.

Liz turned 90 today. It's the lead story on the BBC website, and the usual sycophants are lining up to pay tribute. In fairness, she's tended to keep her nose out of politics, is said to have a good sense of humour and gives good advice. How many people alive today have been in the same room as Churchill and FDR.

The Queen has been "a rock of strength for our nation" and the Commonwealth, Prime Minister David Cameron has said in a tribute to mark her 90th birthday.

The Prince of Wales has recorded a special radio broadcast for the day, in which he reads an edited passage from William Shakespeare's Henry VIII.

Celebrations get under way later as the Queen takes part in a walkabout in Windsor and lights a symbolic beacon.

A photograph of the monarch with young Royal Family members has been released.