Update 24 July 2019 the injunction was partially upheld by the Court of Appeal.
Update 7 June 2018 on 31 May the High Court  EWHC 1330 (Comm)] backed up the CA’s finding with an interim anti-suit (in arbitration) injunction.
In line with my previous post (readers unfamiliar with it may want to refer to it; and to very good Hill Dickinson summary of the case), of particular consideration here is the jurisdictional test under (old) Article 6(1) Brussels I, now Article 8(1) in the Recast, in particular the extent of merits review; and whether the subject matter of the claim comes within the succession exception of Article 1(2)(a) of the Brussels I Regulation.
As for the latter, the Court, after reviewing relevant precedent and counsel argument (but not, surprisingly, the very language on this issue in the Jenard report, as I mention in my previous post) holds in my view justifiably that ‘(t)he source of the ownership is irrelevant to the nature of the claim. ..The subject matter of the dispute is not whether Sana is an heir, but whether the defendants have misappropriated her property.‘ (at 161).
With respect to the application of Article 6(1) – now 8(1), the majority held in favour of a far-reaching merits review. Lady Justice Gloster (at 166 ff) has a minority opinion on the issue and I am minded to agree with her. As she notes (at 178) the operation of a merits test within Article 6(1) does give rise to risk of irreconcilable judgments, which can be demonstrated by reference to the present facts. She successfully, in my view, distinguishes the CJEU’s findings in Kolassa and in CDC, and the discussion at any rate one would have thought, deserves CJEU review.
(Handbook of) EU Private International Law, 2nd ed. 2016, Chapter 2, Heading 188.8.131.52