After the Enigma was cracked, the government was terrified that the Axis would find out. If they knew they were cracked, they could change the cipher and set back the Allies significantly.

So they spent a ton of effort obscuring their own intelligence.

Whenever a decoded Enigma message told them where a U-boat would be, they sent a "spotter" boat whose job is was to be seen seeing the U-boat before it was attacked. That way there was a plausible source of information for the U-boat's location. (These spotters were so "effective", the Germans suspected there must be many more of them in the area then there actually were.)

One time they weren't able to get a spotter there in time and Churchill himself made the call to attack anyway. To cover for that and avoid arousing suspicion, they sent a radio dispatch to a fake spy thanking him for the intel, so that the message could be intercepted by the Germans.

I wouldn't be so confident if I were you.