In farewell speech, Boris Johnson pledges to support Liz Truss ‘every step of the way.’

LONDON — A defiant Boris Johnson defended his three-year premiership but appealed to his party to unite around his successor, Liz Truss, in his final address as Britain’s prime minister on Tuesday morning.

The speech, in which he pledged his own support for Ms. Truss, kicked off a day of closely choreographed events that will see the nation’s top political office transfer to Ms. Truss, the foreign secretary.

“I will be supporting Liz Truss and the new government every step of the way,” Mr. Johnson said speaking from a lectern outside 10 Downing Street, after listing a series of accomplishments by his government including Brexit, the roll out of the coronavirus vaccine and arming Ukraine.

Mr. Johnson made no reference to the scandals that ejected him from office but hinted at his resentment at being ousted, likening the transfer of power to the handing over of a baton in a relay race. “They change the rules halfway through, but never mind that now,” he said.

In a speech that was upbeat in tone, rather than emotional, Mr. Johnson appealed to his fractured Conservative Party to unite. “It’s time for politics to be over, folks. It’s time for us all to get behind Liz Truss and her team and her program and deliver for the people of this country,” he added.

Later he added that, if his pet dog, Dilyn, and the Downing Street cat, Larry, could overcome their occasional differences, so could the Conservative Party.

As for his future, Mr. Johnson was vague, toying with speculation that he harbors ambitions for a comeback.

He was, he said, like “one of those booster rockets that has fulfilled its function, and I will now be gently re-entering the atmosphere and splashing down invisibly in some remote obscure corner of the Pacific.”

A lover of the classics, Mr. Johnson also compared himself to Cincinnatus, a 5th-Century Roman politician who saved the state from an invasion, then retired to his farm. When the call came, he returned to Rome to lead as a dictator.

A crowd of Mr. Johnson’s supporters, including several cabinet ministers, his wife, Carrie, and his sister Rachel Johnson, a journalist, gathered to hear the early morning address, which took place an hour before it had been originally scheduled because of the prospect of bad weather later in the day.

It was Johnson’s last public appearance before he tenders his resignation as prime minister to Queen Elizabeth II later on Tuesday.