Heard this exchange recently on the Heathrow Director frequency:
A/C: "Hello Heathrow, Callsign XYZ descending flight level one hundred to Lambourne, Airbus A319 with information, er, (short pause) Whiskey."
ATC: "Callsign XYZ roger, information Mike is current so your paper must be upside down."
A/C: "Sorry about that, I couldn't see where I'd written it down and I was just guessing."