A question for everyone

Lets see if I can test your knowledge – if I’m sick and tired of the Olympics, there must be others out there as well – and it makes a change from me writing about the DH106 Comet and doing a four volume layout for Martin Bowman!

So…
When did an aircraft get airborne in the UK with three different TYPES of engine at the same time?

And yes, that does make it a six-engined aircraft! (just a little clue there!)

Note!… extra gold stars will awarded to those that can come up with the serial/registration!
Double gold stars if you post a picture – (I already have one, so it’s not a fishing attempt from me!)