Ask HN: Legal advice for a programmer

I have a friend who is caught in an IP issue with their employer regarding a side-project. They told their employer about the project multiple times in detail, and the employer explicitly encouraged and promoted their involvement.

Now the employer has started an investigation because they've learned that the project is taking off and is commercially viable. Whether the employer is trying to defend themselves or something more sinister, my friend does not have a legal contact who can offer advice.

Can anyone recommend my friend a lawyer in the London area?

Following similar advice on HN before, I've told my friend to keep quiet until they've gained legal advice. Are there any other immediate things my friend should do?

Thanks