The inexorably linked worlds of grocery and performance art crossed paths yet again this week.

First as art student Nathan Wyburn wowed judges on Britain's Got Talent with a portrait of Michael McIntyre made from Marmite on toast.

And then street-art legend Banksy appeared to side with the Stokes Croft rioters by painting an ­image of a Tesco Value-branded petrol bomb.

"We're sure Banksy is not advocating violence," bah-humbugged a spokesman for the supermarket.