What is the meaning of the words "substantially the same" in the English Rules of Civil Procedure?

These Rules were taken from English Rules which were nearly identical in wording. The following comments by Lord Hanworth, M.R., in the case of Burford v. Clifford, [1932] 2 Ch. 122 at p. 138, are of assistance: When I come, therefore, to consider the meaning of clauses (b) and (c) of r. 12, sub-r. 1, I think it is plain that the words "substantially the same" which appear in both those clauses relate to the facts which have to be examined for the purpose of ascertaining what is the relief or remedy to which the parties are entitled. "Substantially" must have been put in in order to embrace within the rule something which was not exactly a repetition of the relief or remedy asked for. I think, therefore, that where the same facts have to be conned over in order to ascertain the liability and to give some relief to one or other of the parties, in such a case the rule now provides that it is unnecessary to have separate actions and separate proceedings, but that a third party notice may be served.