UPDATE: Tesla becomes the world's most valuable firm

The American electric carmaker, Tesla, has become the most valuable car firm by market capitalisation - overtaking Toyota to record a total share value of nearly 210 billion dollars. Tesla's share price has nearly tripled this year - despite that fact that it has never made an annual profit. And it's worth noting that Toyota makes around 30 times as many vehicles. According to Susan Schmidt at Aviva Investors in Chicago, market investors love a tech business with the potential for growth.