In the offer document to be posted to shareholders today, Marston is expected to say that if W&D's pounds 262m hostile bid succeeds, it would withdraw its pounds 330m counterbid.
The statement clarifies one of the main uncertainties created by Marston's decision to turn on its suitor with a hostile offer - the so-called "Pac- Man defence".
This highly unusual strategy leaves open the possiblity that both firms could claim victory in their respective bids, declaring their offers unconditional with more than 50 per cent of acceptances. City observers believe that such an outcome could plunge the bid battle into utter confusion as no one would be able to tell whose company had control.
The decision by Marston, famous for its Pedigree bitter and Pitcher & Piano pubs, to withdraw if W&D wins, will be welcomed by the two companies' shareholders, who had been puzzled by the Pac-Man defence.
The move came as the Office of Fair Trading came under renewed pressure by W&D to refer the Marston bid to the Monopolies & Mergers Commission. W&D claims that Marston's plans to close W&D's breweries in Wolverhampton and Hartlepool and to leave the production of W&D's Banks's bitter to Bass would give Bass a dominant position in the Midlands.