Banksy’s mural of three spies appearing to listen in to conversations in a Cheltenham phone booth has been vandalized. According to The Guardian, a name has been scratched onto the sunglasses of the figure on the right side of the phone booth, which could affect the value of the work.

The piece, which has become known as Spy Booth (2014), has been valued at a seven-figure sum and is being fought over by a local community group trying to keep the artwork in the town and a private collector in the United States.

The artwork appeared on the side of a house overnight in April in the aftermath of revelations by whistleblower Edward Snowden that GCHQ, Britain’s intelligence headquarters, and the National Security Agency were involved in large scale surveillance operations.

In June, Banksy confirmed that Spy Booth was his work in the Q&A section of his website. When asked, “Did you paint the spies in Cheltenham?” he replied, “Yes.” Shortly after the admission art collector Sky Grimes contracted Q Scaffolding to remove the wall, claiming he had bought the painting from the owner of the house. The removal was stopped after Cheltenham Borough Council issued a temporary stop notice when it emerged that the mural was painted on a protected, Grade II* listed building.

The artwork can be found on the corner of Fairview Road and Hewlett road in Cheltenham, Gloucestershire. It is located only a few miles away from the surveillance agency GCHQ.