Tesla's share price has tripled in the last six months - can anyone stop it, or even make sense of it?

Ed Butler speaks to Craig Irwin, stock analyst at Roth Capital in New York, who is perplexed by the latest crazy surge in Tesla's valuation, even though he wouldn't particularly describe himself as a Tesla bear. David Bailey, professor of business economics at Birmingham Business School in the UK, says that the optimism is being driven by a growing perception that the electric vehicle revolution may finally be upon us.

But one industry veteran remains hugely sceptical. Bob Lutz has served on the board of all three of America's giant carmakers, and pours scorn on the idea that we will all be driving electric anytime soon.

Producer: Edwin Lane

(Picture: Tesla Roadster launched into orbit by one of Elon Musk's SpaceX rockets; Credit: SpaceX via Getty Images)