Well done Simon. They don't recruit idiots for that job. Beware pilots winding you up - I plead guilty to that one.
In the RAF we used to practise radio failure. When this happens the "carrier wave" is often still available so that if you press the "transmit" button the ATC can hear a "click". To attract the controllers attention you do 4 x clicks to alert them to your presence. They then ask if a speechless arircraft is calling and ask you to respond with 1 x click for "yes", 2 x clicks for "no", and 3 x clicks for "say again". Then they allocate you the callsign of "speechless 1" and ask you a series of questions, like "is this a practise?", "do you have a further emergency" (invariably "yes"), "are you on fire?", "can you maintain height", "do you have a medical problem" etc, with all questions being answered with the appropriate number of clicks.
When I was flying Jet Provosts from Cranwell in the early 1970's 8 of us colluded to return to base simultaneously - all with simulated radio failure - so the poor s** in the tower was controlling 8 aircraft, none of which could speak to him, and with call signs "speechless 1" to "speechless 8". Three of us had practise engine failures and couldn't maintain height, one had a stuck open throttle and couldn't slow down, one had flaps stuck down and couldn't accelerate, and I had a swarm of bees in the cockpit and was periodically flying erratically. You could hear the controllers voice becoming more and more shrill as the stress levels were ramped up without mercy. What fun!