On 9 October 1940 she sailed from Malta to operate in the Gulf of Taranto, with orders to reach Alexandria on completion of her patrol.

For years, it was assumed that Enrico Toti had engaged and sunk HMS Rainbow, which was thought to be operating in the same area.

[2] At 01:00 on 15 October 1940, Enrico Toti sighted a large submarine 1,000 metres (3,300 ft) to port: both boats manoeuvred into attack position.

[3] Famous Italian writer Dino Buzzati, then a very young navy war correspondent gave a lively account of the Triad vs Enrico Toti engagement.

According to sailors' testimonies, the commanding officer of Enrico Toti held his gun fire until he was in a favourable position to launch a torpedo, but both ships were so close that an angered Italian gunner threw his shoes at the head of his British counterpart as he could not yet fire the gun.