The city of Liverpool has officially apologised for flooding a north Wales valley in 1965 to supply water for the city.
Tryweryn, near Bala, Gwynedd, was flooded in 1965 to create a reservoir to provide water for the city.
Liverpool Council members voted unanimously in favour of a motion during a meeting on Wednesday.
The statement acknowledged the "hurt of 40 years ago" and "insensitivity by our predecessor council".
Councillor Mike Storey, the Liberal Democrat Leader of the council, said: "Apologising is the first step towards reconciliation. I hope people don't see it as gesturing because it's not - it's a recognition that mistakes were made."
The flooding displaced the Welsh-speaking community of Capel Celyn and caused bitter political controversy.
An act of Parliament was needed for the compulsory purchase orders for the 800 acres.
The Welsh-speaking village of Capel Celyn was lost in the flooding
The scheme stirred up nationalist indignation and a desperate fight to save the village.
Wednesday's apology came about as a result of an intervention by the Liberal Democrat peer Lord Roberts of Llandudno, who was saddened Tryweryn was cited by many as a reason why the National Eisteddfod should not visit Liverpool.
He approached Mike Storey, leader of the Liberal Democrat-controlled council, who agreed to issue an apology.
The idea has also been backed by the Labour Party, which controlled Liverpool at the time of the drowning of Tryweryn.
The full text of the formal apology reads: "We realise the hurt of forty years ago when the Tryweryn Valley was transformed into a reservoir to help meet the water needs of Liverpool.
Historian Owen Roberts wants the apology extended
"For any insensitivity by our predecessor council at that time, we apologise and hope that the historic and sound relationship between Liverpool and Wales can be completely restored."
Welsh First Minister Rhodri Morgan has welcomed the apology, describing it as a very good step.
Plaid Cymru's Parliamentary leader Elfyn Llwyd said the apology "should be accepted in the fulsome way it is being offered".
But others were less than impressed.
Betty Watkin-Hughes, whose family was forcibly moved from Capel Celyn said: "I think nothing of it, it is just away to say goodbye and sweep it all under the carpet.
"They can keep their apology and start doing what's right for the people who are left."
Owen Roberts, a historian at Aberystwyth University historian, said the council should also apologise for flooding Llanwddyn in north Powys in the 1880s.
The council is considering the Llanwddyn request.