20 August 1962,
The attack on Franco failed in San Sebastian. On the way to the palace of Aiete which the dictator used as the seat of the Guipuzkoan capital, the members of the CNT placed the bomb in a hole on the road of Aldapeta, in order to stop it in its turn. The pump was obtained through ETA. But the batteries lasted seven days and the dictator didn't show up. Before a civilian died accidentally, they decided to disassemble the bomb. Franco came the next day.
Source:
Angel Of Blonde, How to Kill a Dictator. (Ed. Melusina)