The late Queen acceded to the throne 71 years ago, following the death of her father King George VI.
Monday is the anniversary of Elizabeth II’s accession on February 6 1952.
It also marks three months to go until her son and heir King Charles III has his coronation.
Westminster Abbey – the church where the late Queen was married, crowned and where her funeral was staged – commemorated the historic anniversary.
The abbey shared Ralph Heimans’ 2012 painting of the late monarch, which depicts her dressed in her Robe of State and standing in the centre of the church on the spot where she was crowned.
Accession Day is now September 8 – the day the late Queen died at Balmoral Castle and when the King began his reign.
The royal family’s official Twitter account shared a post on Monday from the Department for Digital, Culture, Media and Sport featuring a link to the Coronation website – coronation.gov.uk – and a reminder that the high profile event is taking place in three months’ time.
The May 6 ceremony – which is being held in the abbey – will be a deeply religious occasion, with both Charles and the Queen Consort being anointed and crowned.
