An independent action per Bowen LJ in Amon v Bobbert may proceed despite judgement given P in action or stayed, discontinued or dismissed, just like a statement of claim but here no writ is required failure to file defence to counterclaim results in default judgement given D, principles of statement of claim are applicable to it.
Although writ may be struck out, it doesn’t affect a counterclaim per Adams v Adams where original action struck out for frivolousness but counterclaim succeeds, defence to a counterclaim treated just as a defence to statement of claim, 14 days to file defence to counterclaim, judge gives a two-in-one judgement, for the statement of claim and for the counterclaim. It is treated as across action, properly pleaded and added to defence, not separately: No need repeating facts in defence in counterclaim but be linked.
O 13r8 upon application by affected party court may set aside or vary any default judgement fit, application isn’t time bound but within reasonable time.