Queen Elizabeth, the world's longest-reigning living monarch, celebrates her Sapphire Jubilee on Monday, commemorating 65 years since she took the British throne.

A 41-gun royal salute will take place in central London to mark the occasion. The queen's office released a 2014 portrait showing her wearing a suite of sapphire jewellery she received from King George VI as a wedding gift in 1947.

The Queen, 90, has cut back on international tours but still regularly performs official duties around Britain.

In December she said she would reduce the number of her patronages, passing on her role at dozens of charities, academic institutions and sporting groups to other members of the royal family.

She will spend the day at her residence in Sandringham, eastern England, as is usual, her office said.