Battle lines have been drawn for a hard court tussle in the fight over whether the destruction of the World Trade Centre was one insured event or two.

Leaseholder Larry Silverstein and 20 insurers led by Swiss Re have each set out what they think the towers were worth under Silverstein's cover.

But there is a whopping $4.6bn (£2.98bn) gap between their figures. Silverstein increased his initial estimate from $6.5bn (£4.2bn) to more than $7bn (£4.5bn).

But Swiss Re said the claim's true value was $2.4bn (£1.6bn)and that there were no circumstances under which he could ever recover more than $3.5bn (£2.3bn).

Reports suggested that both sides might be prepared to compromise.