The third decade of The Queen's reign included a number of milestone events, causes for public and private celebration.

In 1977 The Queen marked 25 years as Sovereign. The Silver Jubilee was met with a nationwide tour, Commonwealth visits and celebrations at every level. The Queen and The Duke of Edinburgh travelled 56,000 miles in total to mark the occasion in as many parts of the United Kingdom and Commonwealth as possible.

Jubilee Day, 7 June 1977, was marked by a bonfire chain, a public holiday, and a thanksgiving service in St. Paul's Cathedral. Street parties were held around the country.

The Queen and Duke of Edinburgh celebrated 25 years of marriage in 1972 with a service of thanksgiving at Westminster Abbey. In 1977 they gained their first grandchild, with the birth of a son to Princess Anne.

The Queen's political duties continued as usual. In 1974, The Queen had to fly back from an Australian tour when a general election was suddenly called - it is the only time she has done so.

Following the general election in February, no one party had a clear majority in the House of Commons. The question arose as to whether The Queen should endorse a coalition between the Conservative and the Liberal parties without first giving Labour, the largest party, a chance to form a government. The Tories and Liberals were in the end unable to arrange a coalition, and Harold Wilson returned to power as prime minister.

Later in the decade, The Queen received the first female prime minister at Buckingham Palace, when Margaret Thatcher replaced James Callaghan as leader in 1979.

On the international stage, too, there were several 'firsts'. The Queen paid an historic visit to communist Yugoslavia in 1972, travelled to Hong Kong and then Japan as the guest of Emperor Hirohito in 1975, was the first British Sovereign to travel to the Middle East in 1979, and visited Pope John Paul II in the Vatican in 1980.