It definitely helped that we had both completely compromised the German spy network in Britain, as well as cracking their codes.

The spies let the British feed critical bits of false intelligence to the germans, in a stream of good, if slightly useless or out of date, intelligence.

The breaking of enigma then meant we could monitor, in near real time, how the Germans reacted to it. Limiting the intelligence just enough to make them feel they worked for it, but not so much they missed it.

The culmination was on D-day. Agent Garbo actually messaged the Germans warning them that the landings were on their way to Normandy, before they arrived. However, the British knew exactly how long it would take to actually reach the people that mattered. It arrived just after reports of the landings happening. It was then followed by a panicked warning. The Normandy landings were a diversion, and the main force was leaving for Calais! This kept the German tanks tied up for a critical 3 days.