In a development that has shocked absolutely no one who has ever watched money and politics do their little dance, Reform UK received £72m from two billionaires in a single 24-hour period, and the House of Lords will now debate changes to political donation laws on Monday. The donations came from Ben Delo and Christopher Harborne, both British but with extensive overseas living arrangements, because nothing says "grassroots movement" like two guys who've been chilling in Hong Kong and Thailand.

The government is seeking to change the law on donations from British expats, including a £100,000 cap backdated to 25 March. Because if there's one thing politicians love, it's retroactively changing the rules right after someone else figures out how to win the game.

Unite the Union's general secretary Sharon Graham is among those backing limits on individual donations. Her union has donated large sums to Labour in recent years, but she argues "billionaires splashing out millions" is different from "everyday workers giving 10p a week to a political fund." Which is true, in the same way a firehose is different from a leaky faucet, though both get you wet.

Reform UK's deputy leader Richard Tice told BBC Breakfast the party had done "everything in complete accordance with the laws" and accused Labour of trying to "retrospectively introduce legislation in order to significantly disadvantage another political party." He said the donations would help Reform "get on a level playing field" with other parties, likened it to Labour's union funding, and declared that "competition is a good thing." Spoken like a man who just won the lottery and is now very into the concept of competition.

TUC general secretary Paul Nowak pushed back hard on that comparison, telling BBC Radio 4's Today programme that "trade union money is the cleanest, most transparent money in British politics." He added: "Every decision that unions take about political funding, members decide, it's all in the open. Any conversation I ever have with a minister or a politician, everybody knows what I'm talking about, nobody knows what goes on behind closed doors with Christopher Harborne, Ben Delo and Nigel Farage." Which is a sentence that somehow manages to be both a defence of transparency and a perfect description of a British political thriller.

The bill introducing the £100,000 cap on donations from British voters living abroad returns to the House of Lords on Monday. The rules were proposed in a review by former civil servant Philip Rycroft aimed at countering foreign influence in UK politics. Labour peer Lord Wills told Radio 4's Westminster Hour he intends to amend the bill so donations from those living in the UK could also be capped, because why stop at expats when you can annoy everyone equally?

Reform have said "Labour and their union pals know they can't win an election fairly so now they want to rig the system." Meanwhile, questions remain over whether Reform will actually get to keep all £72m. Robert Jenrick, the party's economic spokesman, told the BBC on Sunday the donations were "entirely in line with the law as it is, and as far as we know, the law as it's going to be in the future." That's the kind of confidence usually reserved for people who haven't read the fine print.

The government has also proposed a minimum residency period in which the £100,000 cap would still apply for those who move back to the UK, in place for the rest of the calendar year and the following calendar year after the person returns. Housing Secretary Angela Rayner told BBC's Sunday with Laura Kuenssberg the rule changes would apply retrospectively and anyone not complying would have "to return that money." Rayner added she wasn't commenting specifically on Delo and Harborne as she did not "understand" their "circumstances" - a diplomatic way of saying she's not touching that one with a ten-foot pole.

The Times reported in June that Harborne, who has been based in Thailand, had registered to vote in the UK, while Delo told the Telegraph in April he was moving back from Hong Kong. BBC News has been told both Delo and Harborne have returned to the UK, with Delo understood to have been back since last year. The government has previously said it was "determined to tackle" the issue of "mega-donors" and has established a new taskforce to do this, because nothing says "we're serious" like a taskforce.

So will record donations to Reform go down as a moment of political change? Only time, and the House of Lords, will tell. But one thing's for sure: £72m in 24 hours is a lot of money, even by billionaire standards. And the debate over who gets to fund British politics is just getting started.