Leaving 10 Downing Street was a political hammer blow for Boris Johnson but is doing no harm to his depleted bank balance.

The former prime minister was paid more than $325,000 for just one speech at a U.S. insurance industry event, according to an updated list of British MPs' register of interests released Thursday.

When he became Britain's leader in 2019, the former journalist was forced to give up a lucrative round of newspaper articles and after-dinner speeches, and got into more than one financial scrape as prime minister.

Forced out in September, Johnson used his new-found freedom to address the Council of Insurance Agents and Brokers in Colorado Springs on October 14.

The speaking fee organised by the Harry Walker Agency in New York came to £276,130 ($325,150), while Johnson and two members of staff also received transport and accommodation expenses.

Just before Colorado, over October 11-12, Johnson was paid £11,559.84 by Rupert Murdoch to fly to a "business meeting" in Montana, where the media mogul owns a cattle ranch.

The U.S. trip interrupted a post-premiership Caribbean holiday for Johnson.

The register showed that on the way out, he, his wife Carrie and their two small children were given luxury lounge space as guests of Gatwick Airport on October 7.

The London airport did the same for them on their return on October 22, when Johnson rushed back from the Dominican Republic to take part in an unexpected new race for the Conservative leadership after the implosion of Liz Truss's premiership.

He gave up the bid the next day, and accepted family accommodation until November 11 from Lord Anthony Bamford, a pro-Brexit businessman who also bankrolled Boris and Carrie Johnson's wedding reception at his country manor house in July.

The ousted prime minister is doing some things for free.

As of October 3, Johnson declared that he is serving in the unpaid role of president of "Conservative Friends of Ukraine", building on his outspoken support as premier against Russia's invasion.

There was nothing listed on the new register for Rishi Sunak, who succeeded Truss last month.

Truss declared a donation of £33,265.48 "to cover winding up costs for my leadership campaign" in July and August. She is now freer to earn outside politics.