The next Netflix movie could perhaps be called, Nightmare in Downing Street, because of the scandal that has erupted over how Boris Johnson paid the £58,000 bill for the redecoration of his grace and favour Prime Ministerial residence.

On Thursday, Boris’s position was made even more uncomfortable by the disclosure that his squeaky clean chancellor, Rishi Sunak, had footed the bill for the refurbishment of his flat in Downing Street from his own pocket.

It has been pointed out that as Infosys founder N.R. Narayana Murthy’s son-in-law and a former hedge fund dabbler, the cost would be small change to Rishi.

As Prime Minister, Boris gets £161,866, plus a £30,000 allowance for his flat, where the decoration is said to have cost as much as £200,000. He probably misses the £250,000 fee he used to get from The Daily Telegraph for a weekly column (which he could knock off in 45 minutes). While the row over Boris’s financial arrangements over the flat is not a resignation matter, those with even a passing knowledge of American criminal history will be aware that the gangster Al Capone was sent to prison for 11 years in 1931, not for the string of murders he had ordered, but for tax evasion.

As the world knows, the British Prime Minister’s official residence is famously 10 Downing Street, while the chancellor of the exchequer, lives next door at Number 11.

But since the flat above No 10 is quite a bit smaller than the one next door, Boris, his girlfriend, Carrie Symonds, and their baby son, Wilfred — he turned one on Thursday — Britain’s First Family have bagged the apartment that Rishi, his wife, Akshata, and their two daughters, Krishna and Anoushka, rightly ought to have. The British Prime Minister and his chancellor basically have done a switch.

Treasury minister Kemi Badenoch told the Commons on Wednesday: “The chancellor redecorated the No 10 flat last year. It was paid for up-front and entirely at his own expense.”

The word “up-front” is significant.

Boris has now paid £58,000 for redecoration after apparently finding the existing furnishings a “John Lewis nightmare”.

John Lewis is a perfectly respectable middle class chain with a flagship store in Oxford Street (which Indian tourists will know well). Some have thought Boris’s alleged remark a trifle “snobbish”, but John Lewis put out a tongue-in-cheek statement: “Time for an interiors refresh? We pride our Home Design Service on having something for *almost* everyone.”The question is over whether £58,000 was given to Boris initially as a loan or a grant from the Conservative Party, which had received a donation of a similar size from a wealthy Tory peer, Lord Brownlow. According to the rules, Boris should have publicly declared any such advance in case donors expect favours in return.

The BBC’s political editor, Laura Kuenssberg, summed up: The question is a simple one. Who paid the bill for the Downing Street flat makeover at the start? And for as long as the PM won’t answer that, the question will be asked again, and again, and again.”

In fact, this has become the main political story in Britain.

Meanwhile, the Electoral Commission, which was set up in 2001 to ensure financial probity in public life, has a launched an inquiry:

“We are now satisfied that there are reasonable grounds to suspect that an offence or offences may have occurred. We will therefore continue this work as a formal investigation to establish whether this is the case.”

A second investigation into the flat will be overseen by Lord Christopher Geidt, a former private secretary to the Queen, who on Wednesday was announced as the new independent adviser on ministerial interests.

The Cabinet Office on Wednesday confirmed the appointment and the probe: “Lord Geidt will begin by ascertaining the facts surrounding the refurbishment of the Downing Street flat and advise the prime minister on any further registration of interests that may be needed.”

The Labour leader, Sir Keir Starmer, has accused the government of being “mired in sleaze, cronyism and scandal”, while in the Commons, Ian Blackford, Scottish National Party leader, asked bluntly: “Are you a liar, prime minister?”

What has made matters doubly difficult for Boris is that his former principal strategist, Dominic Cummings, has come become his deadly enemy after his dismissal last year. He said he had advised the Prime Minister that taking money from donors for his flat was “unethical, foolish, possibly illegal” and that Boris “almost certainly broke the rules on proper disclosure of political donations if conducted in the way he intended”.