Cat Neelan

This is where the party's money gets interesting.

Yeah, that's Poppy Bullard again.

She's speaking to Sam Power at the Observer offices.

They're looking at the Brexit party's financial statement from the end of 2019, essentially its first year of operating.

And it's a peculiar document.

The number they're looking at is a single number in the donations column.

It's £17.2 million.

There isn't really much more detail than that.

No information about who the money came from or what it was spent on.

In terms of donations, we know that around £11 million was declared to the Electoral Commission, and according to Nigel Farage, £5 million came from small donations.

But that doesn't account for it all.

And the number in the expenditure column is even bigger, nearly £19 million.

Even accounting for the fact there were both European elections and a general election that year, Sam Power says the numbers just don't stack up.

We can see from the document that they spent £1.2 million on staffing costs and £9.3 million on campaigning.

But there's another mystery figure in the spending column too.

That's £7 million spent on, well, we have no idea.

And short of someone telling us, no way of finding out.

And the most important thing to note about the Brexit Party's accounting in 2019 is that it's completely legal.

The party isn't required, outside of an election period, to log what it's spent all that cash on, nor is it obliged to say where it came from.

No one we spoke to during the reporting of this story wanted to, or could, tell us what the money was spent on.