The Canadian Prime Minister failed to gain access to Carrick Castle during a tour of the Antrim Coast in February 1961 as the caretaker was having a bath.
The Larne Times reported that John Diefenbaker and his party had to turn back when he failed to open the door.
The Prime Minister and his wife were accompanied by Lord Brookeborough and the High Commissioner for Canada George Drew and Mrs. Drew.
Sergeant S Hodgen, of Carrickfergus RUC Station, said that the group had wished to see round the castle.
However, he indicated that they had rung the doorbell several times without reply.
John Palmer, the castle keeper, said that the castle was closed on Sunday mornings.
“It is usual procedure when any distinguished visitors are coming that I receive prior notice. I knew nothing of this and I am sorry that Mr. Diefenbaker and his party were disappointed.
Mr. Palmer admitted that he had heard the bell but said he believed that it had been rung by children.
At a press conference during his visit to the province, the Prime Minister told reporters that the days of pioneering in Canada were not over and opportunities were greater than ever before.