Art restorer Amy Griffin, from the Simon Gillespie Conservation Studio, says that it should be possible to remove the graffiti without damaging the original painting.
More top news
Tributes have been left in Caledonian Road in Islington where 15-year-old Alan Cartwright died after he was stabbed.
A boy has died after he and his friends were attacked while cycling in north London.
Three police officers have been praised for their actions in helping a four-year-old boy who had become stuck on a roof in Newham.