He also faced questions over the decision to sell the Langham building, opposite Broadcasting House, and build a new centre at White City.

BBC: Obituary: Alasdair Milne

Attacks like the "evil twin" disrupt a company's network from the outside, jamming its radio signals or bogging it down with a denial of service attack, then broadcasting a counterfeit signal into the building.

FORBES: How Lehman Brothers Overcame Its Wireless Fears

Like its cousins radar and sonar, lidar (light detection and ranging), works by broadcasting electromagnetic waves towards a target and then building up a picture from the reflection.

ECONOMIST: Forest conservation

He has said he is building a management team to "deliver a creative vision that will define the BBC and public service broadcasting for the next decade".

BBC: director general Tony Hall 'confident' about future