Chula ambulance

Chula ambulances were vehicles invented by the Chula to heal Chula warriors on the battlefield. They were filled with Nanogenes, and, like all Chula vehicles, could travel in time.

Jack Harkness stole an ambulance and a Chula Warship. He used the ambulance to lure the TARDIS (which he thought contained Time Agents), and he landed it in London 1941. He wanted to con the "time agents" into thinking it was a Chula warship, and made sure a German bomb was to land on it, obliterating it. But little did he realize the Nanogenes would escape, and cause the Empty Child plague.

After this, the ambulance was guarded by the British Army. The Doctor destroyed the ambulance, so it can't cause any more trouble again. (DW: The Empty Child / The Doctor Dances)