One of the first self-service restaurants in Portugal, it opened on April 25, 1973 at Rua Braancamp 9, Lisbon, in the Franjinhas building.

Serendipitously, Sir had a key role in "branding" the Portuguese revolution of 1974 that toppled a 48-year fascist regime. On the 25th of April, 1974 the restaurant was celebrating its first year anniversary and management had bought carnations to offer costumers.

When it became apparent that a revolution was happening, the staff was sent home and some took some the flowers with them. Passing through Largo do Carmo on her way home, Celeste Caeiro, a waiter at the restaurant, came upon revolutionary forces, and when a soldier asked her for a cigarette and she didn't have one, she instead gave him a carnation. He took it and placed it in the barrel of his gun.

The gesture was replicated by others and thus was born the Carnation Revolution.