Held, appeal allowed. Reading CPR r 19.1 with CPR 7.2(1), and with the detailed rules that followed in rules 19.2 to 19.7 about adding, substituting or removing parties, the reference to parties being joined “as parties to a claim” was plainly a reference to a set of proceedings commenced by a claim form, not a reference to an individual cause of action or claim for relief. As CPR 19.1 provided that any number of claimants (or defendants) might be joined as parties to a claim, namely, to a set of proceedings commenced by a single claim form under CPR Part 7 (or equivalent), the CPR provided no absolute limit on the number of claimants on a single claim form. It was not the case that proceedings commenced by a single claim form would only constitute a single “claim” within the meaning of CPR r 19.1 if the CPR r 7.3 test of convenience was satisfied. Instead, if the failure to satisfy that test was of such nature or consequence that the just course was to require the irregularity to be rectified, then the offending claims could be removed from the proceedings, which, in any given case, might or might not involve the removal of parties (paras 42, 43, 46, 71, 85).

(2) There was no requirement that group litigation required one claimant per claim form and the master had erred in law in finding the contrary. Furthermore, difficulties, if there were any, with how CE-File would deal with litigation under the omnibus claim form as issued could not determine the propriety of using such a claim form, which instead turned on the meaning and effect of the relevant provisions in CPR Pts 7 and 19. Accordingly, the master had been wrong to have regard to CE-File practicalities in reaching his decision. He had in any event misjudged those practicalities, there being no evidence that CE-file could not was failing to cope with litigation initiated by an omnibus claim form for the pursuit of claims by large numbers of claimants (paras 19, 26, 31, 32, 35, 37, 40, 86, 87).

(3) The governing principle as to whether a single claim form could be used was not, therefore, whether there were a large number of claimants, but was instead the test of convenience under CPR r 7.3, whereby “a single claim form” ought only to be used to start multiple claims (in the cause of action sense) which could be conveniently disposed of “in the same proceedings”. For that purpose, the proceedings in question were the single set of proceedings which would be commenced by the posited claim form that asserted the multiple claims. In the CPR r 7.3 sense, each claimant on a multi-claimant claim form used that claim form to commence litigation on all causes of action pleaded under it. Convenience of common disposal for the purposes of CPR r 7.3 was not to be equated with case management and rule 7.3 did not require it to be possible or practicable for all claims asserted to be finally determined, if disputed, at one trial sitting. Instead, the governing principle was whether it was convenient for the determination of the multiple claims to be achieved in the same set of proceedings, rather than in multiple sets of proceedings. That did not require common disposal to be the only possible or reasonable way of determining the set of claims in question or that separate disposal would be inconvenient, “convenience” being an ordinary word conveying usefulness or helpfulness in respect of a possible course of action, which did not need further elaboration or lengthy definition. The degree of commonality between the causes of action, including as part of that the significance for each individual claim of any common issues of fact or law, would generally be the most important factor in determining whether it would, or would not, be convenient to dispose of them all in a single set of proceedings. Accordingly, by testing the matter by the impossibility of a single trial determining all the claimants’ military noise induced hearing loss claims (“M-NIHL”) claims in one go, and by setting the commonality bar too high, the master had misdirected himself as to the meaning of CPR r 7.3 (paras 48, 51–53, 62–64, 66, 71, 74, 88).

(4) Whether claims could be conveniently disposed of in the same proceedings within the meaning of CPR r 7.3 was a fact-specific inquiry. In the present case, the question was whether the full cohort of military noise induced hearing loss claims (“M-NHIL”) encompassed by the omnibus claim form, as amended, had sufficient commonality of significant issues of fact that it would be useful or helpful, in the interests of justice, that any determination of those issues in proceedings brought by any one of the claimants against the Ministry of Defence in respect of their M-NIHL injury claim would be binding also as between the ministry and any other of the claimants in respect of their such claim. A non-exhaustive list of questions which were likely to be important across the claims cohort included, in particular, the question of diagnostic criteria for M-NHIL. Given the nature and likely importance to all the claims of the common issues, the proper conclusion, by a clear margin, was that it would be convenient for all the claims to be disposed of in the same proceedings rather than in separate sets of proceedings (whether one set of proceedings per claim, as the master had required, or sets of proceedings in which the claimants were grouped in some way but not so as all to be privy to one omnibus claim form). That remained so even if it were also true, as it might well be, that a final determination of any given claim, if tried on its own, would involve other issues as well (paras 71, 78, 79, 83, 85, 86, 88–90).