BBC director general Tony Hall has received death threats and is now under 24 hour surveillance after the sacking of Top Gear presenter Jeremy Clarkson.
Scotland Yard is investigating the threats made to Hall and his wife, Cynthia, earlier this week.
A spokesman said: "Police in Westminster are investigating an allegation of threats to kill. The allegation was reported to police on Wednesday, March 25.”
"Inquiries continue. No arrests have been made."
On Wednesday, news broke of the BBC’s decision not to renew Clarkson's contract after he abused Top Gear producer Oisin Tymon for “20 minutes” before engaging in a “30 second physical assault”.
The Top Gear programme brings an average of five million viewers and 350 million across the globe.
Hall said at the time: "It is with great regret that I have told Jeremy Clarkson today that the BBC will not be renewing his contract. It is not a decision I have taken lightly.”
Tymon has also received death threats and abuse from trolls on Twitter which North Yorkshire Police continue to investigate.
A BBC spokeswoman said: "We wouldn't comment on security matters."