It looks like even Johnson is claiming he needs to correct the record for misleading Parliament about the parties.

Boris Johnson has promised to address parliament next week about his fine for breaching Covid laws and “set the record straight in any way that I can” on his previous claims that no rules were broken." (Guardian, live report)

This will be an interesting statement. If it restricts itself to the party in which he was fined, a follow up question of "What about the rest?" will be inevitable .On the other hand he certainly won't want to admit to things he hasn't yet been fined for. He will probably go for apologising for the one fine but refusing to comment on the rest, which will not help him much if fines for them do arrive, particularly if his apology claimed to set the record straight.