Hrothgar - the libel action was by the Escort Commander of PQ17, (then) Commander Jack Broome, against the historian (or pseudo-historian) David Irving. Irving's book, "PQ17", implied (or bluntly stated) that Broome's withdrawal was the main cause of the losses to that convoy.

Broome won. All copies of Irving's book were withdrawn from sale (though there may be a few out there). In essence, the signals from the Admiralty gave all commanders concerned the impression that Tirpitz was just over the horizon. Broome went to fight her, not run away from her.

Broome's own experiences of the incident (and some hilarious reminisences of his earlier career) are in his book, "Convoy is to scatter", now probably long out of print.