If an IFR flight experiences complete radio communications failure (Squawk 7600) while in Instrument Meteorological Conditions (IMC) in controlled airspace, what procedure must the pilot follow pursuant to ICAO Annex 2?

1. Immediately turn 180 degrees, descend to sea level, and ditch the aircraft
2. Climb to the maximum service ceiling of the aircraft and hold indefinitely
3. Land at the nearest uninhabited island regardless of terrain or facilities
4. Maintain the assigned speed and level (or minimum flight altitude if higher) for 20 minutes following failure to report over a compulsory fix, and thereafter adjust level/speed in accordance with the filed flight plan, flying to the appropriate navigation aid serving the destination aerodrome and holding until descent