The Court of Appeal will this week hand down its decision on whether insurers should pay compensation to asbestos victims with pleural plaques.
If the judge sides with the claimants in the appeal, insurers could be facing £1.4bn worth of exposures during the next 20 years.
The judgment is also expected finally to lay to rest a long-standing legal battle between insurers and personal injury lawyers over whether compensation is payable in situations where a condition is acknowledged but no negative effects on the claimant's health are apparent.
A spokesman for Norwich Union, one of the insurers involved in the case, said: "While we refute the payment of claims for the 'worried well', we will be relieved to have clarity on the issue, whatever the decision."
Richard Langton, vice president of the Association of Personal Injury Lawyers (Apil), previously described the appeal as "nothing more than a greedy and shameless attempt by insurers to save yet more money at the expense of injured people".