In September 1948, Costello was on an official visit to Canada when a reporter asked him about the possibility of Ireland leaving the British Commonwealth. Costello, for the first time, declared publicly that the Irish government was indeed going to repeal the External Relations Act and declare Ireland a republic. It has been suggested that this was a reaction to offence caused by the Governor General of Canada at the time, the Earl Alexander of Tunis, who was of Northern Irish descent and who allegedly arranged to have placed symbols of Northern Ireland—notably a replica of the famous Roaring Meg cannon used in the Siege of Derry—in front of Costello at an official dinner. Costello made no mention of these aspects on the second reading of the Republic of Ireland Bill on 24 November and, in his memoirs, claimed that Alexander's behaviour had in fact been perfectly civil and could have had no bearing on a decision which had already been made.