Thames Valley Police has released a picture of a man they would like to speak to in connection with shoplifting and common assault in the Iceland store.
At 2.40pm on December 28 the man entered the shop and put a multipack of tinned tuna inside his jacket. As he was about to leave he was challenged by a member of staff who he then punched in the face before running away.
The multipack was later recovered and the victim did not suffer any injuries and he did not need to go to hospital.
Any witnesses can call police on 101 or Crimestoppers, anonymously, on 0800 555 111.