A guilty plea in criminal proceedings can be relied upon as an admission at common law for the purposes of civil proceedings. However the picture is different in cases where a defendant party to a civil claim was convicted of the material act following a trial.
A claimant can rely upon such criminal convictions as establishing a defendant party did indeed assault them during the periods covered by those convictions pursuant to section 11(2) of the Civil Evidence Act 1968.
Of course, applying the civil standard to the alleged acts, it is open to a defendant party to argue that they can prove they did not commit the offence in question (section 11(2) (a) of the Act).
In McCauley v Vine  1 WLR 1977, the defendant contended that her driving conviction was erroneous. Dismissing this argument on the facts, Sir Patrick Russell considered Section 11 holding (see 1981G):
“The closing words of that section “unless the contrary is proved” provides in my judgment, the clearest possible mandate to a defendant in a road traffic accident case to attack his earlier conviction provided he has some good force for so doing and can discharge the burden of proof to a civil standard that the section imposes upon him.”