To demonstrate the power of WiFi Calling, EE held a launch event in the basement of the Imperial War Museum's Churchill War Rooms, of all places.
While we were hoping for cigars and brandy what we got instead was a Samsung Galaxy S6, plus several pounds of metal and concrete.
The thinking behind the location choice was for EE to show off the capabilities of WiFi Calling. As you can see from the picture below, the War Rooms are essentially a series of underground Faraday cages - there's no signal down there whatsoever.
As there was no way we could make a regular call in this environment, we hopped on to the WiFi and waited for the WiFi Calling icon to appear. Once that was good to go, it was a case of just making a regular voice call as usual.
In short, call quality was as good as you'd expect a regular voice call to be. That might not sound like a lot to write home about, but we've experienced our fair share of similar services in the past, and there's often been a noticeable drop in call quality.
Our trained ears couldn't detect any huge difference between WiFi calls and regular network calls on the Galaxy S6.
There were a couple of hiccoughs when we first tested the service out in the War Rooms.
But as anyone who has attended a press briefing, conference or convention will tell you, event WiFi is always flaky at the best of times, something not helped by a room full of journalists all trying to connect at the same time.
We've not experienced any such slip ups since when testing it out at home or out and about, so we're going to put that down to crowded WiFi.
In areas where there's plenty of people all clamouring to use the same access point - like on the London Underground, train stations, festivals - it's possible that WiFi Calling could run into similar issues.
We've been testing the service out at home and on (markedly less busy) public WiFi networks over the Easter weekend and found that the service worked just fine. If we encounter any issues in future, we'll update this piece.
One thing we did experience when testing this out was calls dropping whenever we walked out of range of the WiFi signal. EE has yet to perfect the handover process, which will see you able to start a voice call on WiFi and then continue the same call on the regular mobile network, and vice versa.
We understand that you'll be able to do this following the arrival of VoLTE (Voice over LTE) or '4G calls', which is due to be launched by EE later this year.
For more information on EE WiFi Calling, which phones it's coming to and how to get it, check out our in-depth 'Everything you need to know' feature