The Head of State was accompanied by the Portuguese Ambassador in London, Nuno Brito, and by the Head of State Protocol, Clara Nunes dos Santos.

The President will then sign the official Book of Condolences at Lancaster House before attending a reception at Buckingham Palace hosted by King Charles III for international leaders who travelled to witness the state funeral being held on 19 September.

Thousands of people have waited up to 24 hours in recent days to enter the site and pay their last respects, creating a queue up to 8kms in length.

Today at 20:00, the United Kingdom will observe a minute of silence as a "moment of reflection" in memory of the monarch, who died on September 8 at the age of 96 after 70 years on the throne.