As they drank they pondered how to celebrate May Day the following day.
Then one of them came up with an idea. Why not go up The Wrekin and plant the red flag on top?
The new Labour leader told the story in a recent interview – and confirmation of the escapade today came from Peter Harrison of Wellington, who was chairman of Wrekin Young Socialists at the time that young Jeremy was secretary.
He said: "We used to meet in the Raven in Wellington where there were a series of old rooms, and the landlord allowed us to use one of them. We were all young and idealistic people, pretty much as Jeremy is now. We were drinking and it was May Day the following day, and asking what we were going to do to celebrate, and next thing you know one said, 'Why not go up The Wrekin and plant the red flag?'
"If I remember correctly one of them made the red flag and we took it to the top of The Wrekin and tied it to the trig point and we all sang the Red Flag and came down, and went to the Raven and had a few more pints. I'm not sure what happened to the flag. We did it just the once.
"There were 50 members of the Wrekin Young Socialists, largely down to Jeremy Corbyn's activity. He was a born organiser.
"What you see now is what you get. I knew him when we were 18 or 19, and his views have not changed. We are talking about the thick end of 50 years ago."
Peter also remembers Mr Corbyn's short time as a reporter for the Newport Advertiser, adding: "He covered funerals, and got as many names as he could.
"The editor told him that if you get the names in, they will buy the paper. And then he was involved in politics.
"I can tell you this much about him: he ate, dreamt, and slept politics."