It's not clear that the "the Met Police [was] briefing the BBC before contacting interested parties", as Tice suggests.
According to the BBC article in the OP, the BBC were following up a Guardian report on two payments by Tice's Britain Means Business company to Reform in 2024, when Tice was Reform chairman.
The Guardian reported that the two payments from Britain Means Britain were among four flagged to the National Crime Agency as part of its Suspicious Activity Reports programme. (The other two flagged payments were made to Reform directly by Fiona Cottrell and were reported on by The Times.)
The BBC then approached the Met and asked for comment:
Asked about the donations from Britain Means Business, the Met repeated a statement originally issued earlier this month after The Times's investigation.
A spokesperson said: "An investigation was launched in February 2025 after a referral was made to the Metropolitan Police by the Electoral Commission relating to donations made to a political party ahead of the 2024 UK General Election."
They added: "Detectives from the Met's Special Enquiry Team are investigating alleged offences under Section 61 of the Political Parties, Elections and Referendums Act 2000.
"Early investigative advice has been sought from the Crown Prosecution Service and two people have so far been interviewed under caution. No arrests have been made.
"An offence under this section is not one that the Electoral Commission can investigate and, as such, it is a matter for the police."
https://www.bbc.co.uk/news/articles/c5yv4r5g55do
So (1) it seems the Met haven't gone out and briefed the BBC, merely responded to the BBC's query.
And (2), if the Met interviewed two people under caution several weeks ago, for large donations made by Richard Tice's company Britain Means Britain to the political party Reform of which Richard Tice was chairman, how likely is it that Richard Tice hadn't even heard of the investigation until asked by the BBC yesterday?