Queen Elizabeth II on Friday celebrated 63 years on the British throne as she neared the record set by Queen Victoria for the longest-reigning monarch.

She was to mark the occasion privately at her estate in Sandringham, southeast England, where she spends her annual winter break.

There will be a 41-gun salute by the King's Troop Royal Horse Artillery in London's Green Park, and a 62-gun salute by the Honourable Artillery Company at the Tower of London.

Elizabeth became queen aged 25 when her father, King George VI -- subject of Oscar-winning film "The King's Speech" -- died from a coronary thrombosis on February 6, 1952.

The 88-year-old monarch, who will break her great-great-grandmother Victoria's record on September 9 this year, was on a tour in Kenya at the time of her father's death.

Victoria reigned for 23,226 days, 16 hours and 23 minutes, taking into account the exact timings of her accession and death.

Before she breaks the record, the queen will welcome the Mexican president for a state visit, and herself make a three-day state visit to Germany.

She is also anticipating the arrival of grandson Prince William's second child in April.