Protester Anna Holland says her shock at being behind bars was quickly followed by a stronger feeling of power

• Record number of protesters will be in UK prisons this Christmas

Anna Holland, 22, was one of two young people from Just Stop Oil who threw tomato soup over the Sunflowers painting by Vincent van Gogh – one of the highest-profile climate protests of recent years. The painting was not damaged although there was damage to the frame. Holland was sentenced to 20 months in prison. She sent this letter to the Guardian about her experience behind bars.

“It was a shock at first that the judge had gone to the extreme of our sentence. The first few days and nights in prison were hard but also such an education. So many of the women I have met here are in prison because they were not properly protected by the state, so they have taken me under their wing. I have been looked after, taught the ways of prison, not by the staff but by the other prisoners. It is like nothing I had expected and it is completely overwhelming – but also surprising how quickly I found myself falling into the daily routine.