The Court of Appeal has handed down its judgment in London Borough of Enfield v Sivanandan - a highly complex decision.
Ignoring the facts completely, the principles that can be extracted are:
(1) if a breach of contract claim is struck out (rather than withdrawn) by an employment tribunal, it is an abuse of process to re-issue it in the High Court. The rule in Sajid v Chowdhury 2001 (reported at  IRLR 113, CA) - i.e. that a Claimant can withdraw a contract claim and re-issue in the High Court to avoid the £25,000 cap on damages - does not apply if the employment tribunal claim is struck out (judgment para. 120)
(2) if a Claimant wishes to withdraw such a claim in the employment tribunal, it is incumbent on the tribunal to record the position on the face of the decision (para. 122) - and thus incumbent on the Claimant to ASK the tribunal to record the reason for withdrawal on the face of the decision.
(3) even where a breach of contract claim IS properly withdrawn in the employment tribunal, it is nevertheless an abuse of process to re-issue it in the High Court if existing claims in the employment tribunal cover the same facts and have unlimited compensation. In Sajid (above), the Applicant could not recover unlimited damages OTHER than by re-issuing his claim in the High Court. If a Claimant in employment tribunal proceedings was also claiming discrimination in respect of the dismissal, which carried an uncapped award, it is open to a tribunal to award compensation reflecting a Claimant's real losses. Since there is no need for the Claimant to withdraw and re-issue a breach of contract claim, to do so is an abuse of process judgment, para. 133)
A word of warning: do not read this decision unless you are willing to risk a major headache.