John Wood Group PLC shares rose almost 10% after its board decided to engage in takeover talks with Sidara.
This followed a fourth possible offer from the Dubai-based rival at a "final price" of 230p per share in cash.
Wood's board said that while it "remains confident" in the current strategy and prospects, "having now weighed all relevant factors including, in particular, feedback received from Wood shareholders, the board has decided to engage with Sidara to determine if a firm offer can be made".
Sidara is being given access to the books to carry out due diligence and the put-up-or-shut-up (PUSU) deadline has been extended to 5pm on 3 July.