Thank you 20 Essex Street for flagging (and analysing)  EWHC 3009 (Comm) Qingdao Huiquan, granting anti-suit against a foreign litigant who is not a party to an exclusive choice of forum agreement (in particular: arbitration agreed in a settlement agreement). The third party, SDHX, is engaging in proceedings in China, and is related to one of the parties to the settlement agreement.
SDHX appeal to privity of contract is tainted by its invoking elements of the settlement agreement in the Chinese proceedings. Under relevant authority, this was ground for Bryan J to issue aint-suit against it.
A classic cake and eating it scenario, one could say: at 36: ‘I have had particular regard to the fact that it is clear from the Settlement Agreement that SDHX is indeed seeking to rely upon the terms of the Settlement Agreement in advancing its claims in the Chinese proceedings and that, in doing so, therefore, it has to take the burden of the arbitration clause, if an arbitration clause be a burden,..as well as the benefits that it seeks to derive from that agreement.’ (Update 19 April 2019 a principle known as equitable estoppel which was recently also applid by the South Carolina Supreme Court in Wilson ea v Willis ea 2019 WL 1549924 on wich more here).
eEvidently Brussels I Recast is not engaged.
European private international law, second ed. 2016, Chapter 2, Heading 188.8.131.52.