Hammersmith Magistrates’ Court heard that large adverts for London Basement Ltd were displayed at 72 and 44 Scarsdale Villas in Kensington, where the company was carrying out basement extensions for the homeowners.

There were 22 adverts on 72 Scarsdale Villas with an aggregate size of 42 square metres and five adverts on 44 Scarsdale Villas with an aggregate size of six square metres.

The court heard it is a criminal offence for a developer to display more than one advert on a building site in a conservation area unless it first receives consent from the local council.

The advert can also be no greater than two metres square in area.

The company was warned in May 2014, by the Royal Borough of Kensington and Chelsea’s Planning Enforcement Team, to remove all unauthorised adverts from within the borough or face prosecution.

The company did so but was witnessed displaying unauthorised advertisements on dates between September 2014 and March 2015.

The court heard how the company had no previous convictions and had taken steps to ensure advertisements on other sites it was working on complied with all regulations.

London Basement pleaded guilty and was fined £12,334 with costs of £2,980 and ordered to pay a victim surcharge of £120.

Councillor Timothy Coleridge, the Royal Borough of Kensington and Chelsea’s Cabinet Member for Planning Policy, said: “We will not allow developers to advertise themselves illegally in our residential areas.

“We will take action and go to court if required.”