WOULD-BE artists painstakingly numbered the volumes of a sculpture in Oxford’s Bonn Square — but ran out of energy when they reached the number 20, using a mixture of Arabic and Roman numerals.

The sculpture was unveiled in May during celebrations to mark the reopening of the square after a £2m facelift.

Officials from Oxford’s German twin city Bonn commisioned the sculpture by Boars Hill artist Diana Bell as a gift to Oxford.

Ms Bell said: “Someone has spent a lot of time thinking about this and I’m interested to see that they wanted to add something — it’s not really graffiti.”

City councillor Colin Cook, whose responsibilities include the city centre, said: “This was probably childish behaviour, rather than a serious attempt to damage the sculpture, but we don’t welcome this sort of thing because it encourages similar behaviour and worse.”

Headington resident Stephanie Jenkins, who spotted the grafitti, said: “They have numbered the volumes with what looks like white paint and then written at the bottom ‘Books aren’t worth it’. They haven’t written anything particularly witty – I don’t know why they bothered.”

City council staff were called in to clean off the writing.