The letter fell softly on Lynne and Mark Wilkinson's front door mat but its contents were anything but light.

It informed the couple that they owed almost #24,000 in debts dating back more than 13 years.

Like thousands of other families, they had bought a home at the height of the property boom of the late 80s then run into financial trouble at the start of the property crash.

The pair had defaulted on their West Bromwich Building Society mortgage repayments and eventually had their Norfolk house repossessed. That was in 1989.

Fast forward to 2002 and they thought that sad chapter was behind them.

However, the nightmare started again when the WBBS demanded they pay what it believed they still owed.

To cancel their debt, the Wilkinsons started a legal battle that would take them to the highest court in the country ? the House of Lords.

Now they have won, their victory against the West Bromwich could mean hundreds of mortgage borrowers who suffered in the property crash could have the debts claimed by their building societies written off if they date back more than 12 years.

The law states that a building society can chase debtors for up to 12 years, but until the ruling in the Wilkinsons? favour it has been unclear at which point that period should start.

WBBS believed it was 12 years after the date of the house sale.

The Wilkinsons, however, thought it should have been 12 years from when they stopped paying the mortgage.

Their lawyer, Stephen Murrell, a senior partner at London firm Staple Inn Partnership Solicitors, said: ?An awful lot of people out there will be very interested in the outcome of this case. They may want to know whether their debts fell before or after the 12-year period.

?Cases will now either go forward because they are within the 12-year limit or have to be dropped.?

He urged those who think they may not have to pay off their debt to seek legal advice.

He said: ?Ordinarily people have a month in which to appeal. However courts, depending on the circumstances, will allow appeals much later.?

A spokesman for the West Bromwich Building Society said: ?In all cases we are sympathetic to any member who finds difficulty in meeting their financial obligations and we seek every avenue to ensure that repayment of any outstanding debt is concluded by a mutually satisfactory agreement.

?This decision has now clarified the date from when the period will run during which bad debt recovery claims can be made. It relates only to the recovery of bad debts, all of which were provided for, and, therefore, the ruling will have no cost or other adverse financial implications for the society.?