Shocked: Dr Chris Townley was charged a commission and fees by Foxtons for the light fitting to be replaced

Stock market listed estate agent Foxtons could face a legal bill of as much as £42million after charging a landlord a total of £616 to change a light fitting.

In what could be the most costly light replacement in history, solicitors believe the dispute could lead to Foxtons being sued by thousands of landlords regardless of whether they have had work carried out at their properties.

Foxtons used a subcontractor called Maintenance1st to do the work. Dr Chris Townley was billed £550 plus £66 VAT, but he later found that the subcontractor had charged much less.

Dr Townley, a law lecturer at King’s College London, signed up with Foxtons to let and manage his London property in 2011.

In 2013, he was sent a bill for the repair, but he demanded a refund after complaining that the work was substandard. Maintenance1st disputed this and did not refund Dr Townley.

The estate agent had reluctantly put him in touch with Maintenance1st, which told him its charge for the work was £412.50.

When challenged on the difference, Foxtons admitted it had added a £137.50 commission – 33 per cent of the subcontractor’s fee. Dr Townley also discovered that Maintenance1st had paid Foxtons an undisclosed commission for undertaking the work.

Additionally, Foxtons had charged Dr Townley an ‘ad hoc management charge’ of 10 per cent plus VAT because the invoice was over £500 despite the fact that the only reason it exceeded this sum was because of Foxtons’ 33 per cent fee.

In total, Dr Townley had to pay Foxtons fees of £203, which was a 49 per cent mark-up on the original £412.50 invoice.

Leigh Day solicitors has served the estate agent with a letter of claim, which is sent prior to the beginning of legal proceedings, alleging the ‘hidden commission’ was not covered in the landlord’s contract.

Allegations: Stock market listed estate agent Foxtons could face a legal bill of as much as £42million after charging a landlord a total of £616 to change a light fitting

It says thousands of other landlords will also be entitled to compensation from Foxtons and it believes claims could reach £42 million.

Dr Townley said: ‘When I first heard there was a commission I was not happy, but thought it may be 2 or 3 per cent. When I found out the real amount I thought it was shocking.’