The Welsh Language Society's first protest in Aberystwyth
An appeal has been launched to track down campaigners who took part in the Welsh Language Society's first ever protest 45 years ago.
The National Library of Wales wants to record memories of what happened on Aberystwyth's Trefechan bridge in 1963.
About 40 people took part in what started a Welsh language campaign.
Lecturer Rhys Jones, who has written about it, said the sit-down protest had not been planned and campaigners had wanted to target a post office.
Dr Jones, of Aberystwyth University's geography department, said: "The protest was not supposed to have taken place on Trefechan bridge.
"The plan was to place posters on the town's post office and have a few protesters arrested.
"Being arrested meant they would receive a court summons in English, which the protesters would then refuse to recognise.
"But the police somehow knew about this and went out of their way not to arrest anyone, and as far as I'm aware no-one was arrested that day.
"On their way back from the post office, protesters decided to sit down on Trefechan bridge."
Dr Jones' book Placing the Nation, which was co-written with Carwyn Fowler, deals with Aberystwyth's role in shaping nationalism in Wales.
He said the protest led to courts in Cardiff, and later around Wales, issuing summons' in Welsh on demand.
The protest was inspired by a 1962 radio lecture by Saunders Lewis, a former president of Plaid Cymru, called Tynged yr Iaith/The Fate of the Language.
It led to the formation of Cymdeithas yr Iaith Gymraeg (Welsh Language Society) a year later.
A spokeswoman for the library said: "The library would like to find out who are the people in the photograph - the protesters and the local townspeople who happened to be present."
People involved in the protest or in the crowd are asked to contact Medi Jones at firstname.lastname@example.org or on 01970 632534.