Biggest coincidence in recent memory is probably there being terror drills going on the same exact targets as actually occurred during the 7-7-2005 bombings in London:
P.S. I am not saying there was a conspiracy or something, it should rightfully go down as the biggest coincidence in recent memory, however.
2 weeks ago I was sitting in the train to Amsterdam when the train had to make an emergency stop at a small village because fire had broken out in the electronics system in the front of the train. At that very same moment emergency services were practising in that same village, less than 100 meters away from where the train had stopped. They were practising... their communications in case of a train fire.
Coincidence?