Resumen: The article first seeks to identify the lessons different versions of the British left drew from the end of Popular Unity and the subsequent installation of the military regime in Chile, under a government led by the Labor Party. Likewise, it attempts to shed light on how British solidarity with the Chilean cause made it possible to unite and give collective meaning to this divided left, sometimes plagued by infighting, representing an exceptional case in the Western European scenario. To this end, the collections of Judith Hart and the Chilean Solidarity Campaign in the Labor History Archive, in Manchester, and the Foreign Office documents in the British National Archives were reviewed. This was complemented by secondary bibliography and interviews with key informants.