Liz Truss Photo: Xinhua

Boris Johnson on Tuesday promised unswerving support for his successor Liz Truss, as he left Downing Street for the final time as British prime minister to tender his resignation.

Johnson, whose tenure was dominated by Brexit and COVID-19 and cut short by scandal, bid farewell to cheers and applause from supporters before heading for an audience with Queen Elizabeth II.

In a typical rhetorical flourish, he likened himself to "one of those booster rockets that has fulfilled its function" and he would now be "gently re-entering the atmosphere and splashing down in some remote and obscure corner of the Pacific."

But he promised: "I will be supporting Liz Truss and the new government every step of the way."

And he urged his ruling Conservative party to put aside their differences to tackle the energy crisis that looks set to dominate Truss's immediate future.

"If Dilyn [his dog] and Larry [the Downing Street cat] can put behind them their occasional difficulties then so can the Conservative party," he said in a statement.

Normally the handover of power in Britain is a swift affair, with the outgoing and incoming leaders making a short trip to Buckingham Palace in central London in quick succession.

But both Johnson and Truss face a 1,000-mile (1,600-kilometer) round trip to the head of state's remote Balmoral retreat in the Scottish Highlands.

The queen opted not to return from her annual summer break for the brief ceremonial audience, after persistent health issues that have affected her ability to walk and stand.

After the formalities with Johnson, she will ask Truss, as the leader of the largest party in parliament, to form a government and be the 15th prime minister of her 70-year reign.

The "kissing of hands" ceremony has not taken place at Balmoral since 1885, when queen Victoria summoned Lord Salisbury to the Highlands.

It has only happened once outside London since 1952, when Winston Churchill met the new queen at Heathrow Airport after the death of her father, king George VI.

Truss, 47, was announced winner of an internal vote of Conservative party members on Monday, after a gruelling contest that began in July.

She is expected to make her first speech as prime minister outside 10 Downing Street on Tuesday afternoon - weather permitting.

Heavy rain and storms are forecast, mirroring the gloomy economic situation that she and her new senior ministers will have to tackle from day one.

The appointments are due to be finalized before she hosts her first cabinet meeting and faces questions in parliament on Wednesday.

Business Secretary Kwasi Kwarteng is expected to become finance minister, with Attorney General Suella Braverman moved to the tricky brief of home secretary, and James Cleverly to foreign affairs.

AFP