The worker was on the Circle Line and preparing to get off the train at High Street Kensington when he approached the man and challenged him about not wearing a mask.
He was then pushed off the train and onto the platform, while the man continued to punch him.
Sustaining a chipped jaw and three breaks to his eye socket, the victim now needs permanent metal plates in his face.
Police put out an image on Monday’s Crimewatch Live of a man they would like to speak to in connection with the attack.
He is described as a white man in his 20s with blonde hair that was short at the sides and longer on top, clean-shaven, and wearing a navy-blue suit and light blue shirt. He was carrying a large green umbrella and grey rucksack with a blue Nike logo.
Anyone who recognises the man or has information can contact BTP by texting 61016, or call 0800 40 50 40, quoting reference 2000068891.
Alternatively, they can call Crimestoppers anonymously on 0800 555 111.
Crimewatch Live is on BBC One and BBC iPlayer weekday mornings at 11am until Friday, March 26.