The railway runs alongside the River Dee

The benefactor has also offered to pay back 10p for every �1 the trust can raise against the loan by September this year.

The overall cost of the viaduct project, situated in the Vale of Clwyd, is �365,000.

The Llangollen Railway Trusts's appeal has already raised more than �15,000 since its launch last year.

Money for the project will also be received through Objective One, a European fund to help regenerate parts of Wales.

The project funding will allow the track to be removed over the viaduct, the replacement of the waterproof membrane, which protects the viaduct, and the stabilising of the structure.

It is expected the work will take around two months to complete.

The trust has also finalised the renewal of the lease for the railway for a further 55 years from Denbighshire County Council.

The work will see the viaduct return to it's former glory

Frank Spence,Llangollen Railway Trust

This will allow another �525,000 to be spent on renovating the Llangollen and Berwyn stations.

This will be funded with a Heritage Lottery Fund grant for �404,000 which was conditional on the railway being granted a lease of more than 25 years.

The original offer in 1996 was for �299,000 and represented 72% of the cost.

Major investment

The Heritage Lottery has added another �105,000 to take into account the revised project costs.

The trust already has �121,000 in place for this scheme which brings the total investment in the railway to �825,000.

Frank Spence of the Llangollen Railway Trust said: "The work will see the viaduct return to it's former glory with the reinstatement of the platform extension.