Adelphi

The Time Lord messenger, or the "Bowler Hat Time Lord", was a Time Lord who often travelled to Earth to warn the Third Doctor about events.

Biography
He first met the Third Doctor when he appeared in his TARDIS, while he was with Liz Shaw. (AUDIO: Shadow of the Past)

The Doctor next met him when he was sent by the Time Lords to tell the Doctor about the arrival of the Master. (TV: Terror of the Autons)

He was sent to see the Doctor again for a third time, with Sarah Jane Smith, when he had to persuade the Doctor not to travel with a future companion, before he actually began travelling with him. (PROSE: An Overture Too Early)

Profile
He was dressed as an English businessman, complete with bowler hat and umbrella. His disguise was somewhat compromised by his first being seen to hover in mid-air, due to his co-ordinates having "slipped". He warned the Doctor that his (the Doctor's) old enemy,, had arrived on Earth and might try to kill him. (TV: Terror of the Autons)