A widower has won a test case at the UK's highest court to change a law which has led to many dependants of people who have been "wrongfully killed" being under-compensated for their loss.
Lawyers for Ian Knauer, from Dorset, whose wife Sally died as a result of exposure to asbestos at work, say the decision of seven Supreme Court justices "is likely to cost the insurance industry millions in extra damages each year".
The panel of judges, headed by Supreme Court president Lord Neuberger, ruled there was "an overwhelming case for changing the law" relating to the way financial losses of dependants are assessed.
In July 2014, Mr Knauer won High Court damages totalling £647,840 after making a claim for future loss of dependency under the Fatal Accidents Act 1976.
Mother-of-three Mrs Knauer, who contracted mesothelioma, died at the age of 46 in August 2009. She was exposed to asbestos at Guys Marsh Prison, Shaftesbury, Dorset, while employed as an administrative assistant.
The damages were awarded against the Ministry of Justice (MoJ), which admitted liability.
Law firm Charles Lucas & Marshall, which represented Mr Knauer, said the Supreme Court's ruling "will change the law for fatal accident cases in the UK" - covering medical negligence, industrial disease and fatal road traffic accident claims.
The solicitors said that "many claimants" had been "grossly under-compensated", and added: "In future, multipliers which are used to calculate the compensation amount will be calculated from the date of trial, not the date of death.
"It will mean that all claimants will receive greater sums to compensate for loss of income and services."
The Supreme Court judges unanimously allowed an appeal by Mr Knauer over the way compensation has been assessed to date.
Lord Neuberger and the court's deputy president Lady Hale, giving the ruling of the court, explained: "The issue in this case is whether the current approach to assessing the financial losses suffered by the dependant of a person who is wrongfully killed properly reflects the fundamental principle of full compensation, and if it does not whether we should depart from previous decisions of the House of Lords."
They said the House of Lords cases - in which the approach was to calculate the multiplier from the date of death - "were decided in a different era, when the calculation of damages for personal injury and death was nothing like as sophisticated as it now is".
Lord Neuberger and Lady Hale said that "at least in the current legal climate", the application of the reasoning in those previous decisions "is illogical and their application also results in unfair outcomes".
The aim of an award of damages "so far as possible" was to "place the person who has been harmed by the wrongful acts of another in the position in which he or she would have been had the harm not been done: full compensation, no more but certainly no less".
They added: "Of course, there are some harms which no amount of money can properly redress, and these include the loss of a wife or husband.
"There are also harms which it is difficult to assess, especially those which will be suffered in the future, but the principle of full compensation is clear."
The judges rejected a suggestion that rather than the court changing the law, it should leave it to the "legislature to do so".
They said: "The current law on the issue we are being asked to resolve was made by judges, and if it is shown to suffer from the defects identified... then, unless there is a good reason to the contrary, it should be corrected or brought up to date by judges."
In conclusion, they said the "correct date as at which to assess the multiplier when fixing damages for future loss in claims under the Fatal Accidents Act 1976 should be the date of trial and not the date of death".
Lord Neuberger and Lady Hale said the parties agreed that in Mr Knauer's case "the difference between the two approaches is £52,808".
Brigitte Chandler, of Charles Lucas & Marshall, said: "Our client Mr Knauer did not bring the appeal for the sake of getting more damages, but to help other people who will have to bring claims in the future.
"He felt, as a result, perhaps his wife did not die from mesothelioma in vain and she was able to help future claimants."