s 18 Exclusion of other jurisdictions
18.—(1) Where an action on a claim (called in this section the firstmentioned proceedings) is commenced in a tribunal, no other civil proceedings relating to that claim (called in this section the second‑mentioned proceedings) may be commenced in any other court except —(a) where the second‑mentioned proceedings were commenced in that other court before the firstmentioned proceedings were commenced in the tribunal; or (b) where the claim before the tribunal is withdrawn, discontinued or abandoned, or is dismissed for lack of jurisdiction. (2) No action for a claim may be brought before a tribunal if civil proceedings relating to that claim are pending in or have been heard and determined by any other court.