Can you tell me more about that and how to establish jurisdiction in Britain and also collect upon winning?

Are judgements in Britain worthwhile, monetarily?

Peter McCormack appears to live in the UK[1], so establishing jurisdiction is straight forward.

Libel damages vary - £24,000, £40,000, to a few hundred thousand[2] - it depends on the facts of the case (though the loser will also have costs to pay).

[1] https://uk.linkedin.com/in/petermccormack1

[2] https://www.pressgazette.co.uk/food-blogger-jack-monroe-wins... ; https://www.lawgazette.co.uk/law/40000-damages-in-twitter-li... ; https://en.wikipedia.org/wiki/English_defamation_law#Damages