Rakeem Miles, 23, followed Samuel Winter, 28, after he brushed past on the escalator out of Southwark Station.
After Samuel had walked through the ticket barriers Miles grabbed him from behind and punched him in the head, leaving him collapsed on the stairs.
Paramedics were dispatched to the scene where Samuel was given CPR before being taken to hospital where he died on August 23, the day after the incident.
Police tracked Miles to a shop where he had topped up his Oyster card only to discover that he had just left.
They arrested him nearby on suspicion of grievous bodily harm, a charge which was then upgraded to manslaughter when Samuel died.
Miles was convicted of manslaughter on March 21 after a trial at Inner London Crown Court.
Samuel’s family said: “We have lost our gentle, hugely compassionate, funny, intelligent and hard-working son Sam because of this entirely unprovoked and horrific assault.
“We would do anything and give everything to have Sam back with us. But he’s gone for the rest of our lives.
“The pain of his loss is almost unbearable for us, his wider family, many friends and all the people in his community, whom he loved to help through his physiotherapy, service and personal generosity.”
Det Chf Insp Paul Attwell said: “This was a truly tragic incident where one person’s actions and one punch has changed the lives of Samuel’s family forever.”
“It only took one punch from Miles to end Samuel’s life and forever change the lives of those around him. He showed no remorse for his action, leaving Samuel at the station and continuing on with his evening.
“The quick-time and thorough investigation by the teams involved meant Miles was identified and apprehended quickly. There is zero tolerance for violence on the railway and I’m glad to see this conviction.”
A sentencing date has been set for May 8 at Inner London Crown Court.
