Shares in Sainsbury's rose 15.5p to finish on 569.5p yesterday after the supermarket chain said it would open its books to Qatari-backed Delta Two for due diligence.

Sainsbury's chairman Sir Philip Hampton also said that if Delta Two made an offer following due diligence, it “would be recommendable to shareholders”.

Any possible deal, following months of talks, was still too close to call, analysts said. “I don't think it's a done deal,'' Freddie George, an analyst at Evolution Securities, told Bloomberg News. “If Delta finds something they don't like during due diligence they could walk away and come back with a lower offer next year.''