A Suffolk woman was one of four people to be arrested after milk was poured onto M&S' employees and shop floor in Norwich city centre.
Police were called to the incident in the Rampant Horse Street just before 12pm on Saturday, where Animal Rebellion protestors were protesting.
Officers were called to reports that four people had entered the shop, picked up cartons of milk from the fridge and poured the milk over displays of milk, meat and pizza.
It is also understood that milk was poured over two Marks & Spencer employees after they challenged the protestors.
After the protestors left the shop they were located by officers from Norfolk police outside Norwich train station.
Two women aged in their 30s from Norfolk, a man aged in his 40s from Essex and a woman aged in her 40s from Suffolk were arrested in connection with the incident and taken to Wymondham Police Investigation Centre for questioning.
They have all been released on police bail until November 12.
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