Sarah Arnott: £40bn lost, and US drilling in doubt until 2017

The company

BP's rollercoaster ride since the Gulf of Mexico disaster has seen more than £66bn wiped off its share value – and another £20bn regained – against a background of vilification, political pressure and rampant takeover rumours.

The clearest index of trouble is the stock price. Shares selling for £6.55 before the explosion on 20 April dropped a staggering 54 per cent in value.

Even now, after rebounding by more than 35 per cent since the first partial success in capping the stricken well, the shares are still worth little more than half pre-disaster levels.

But BP's problems are greater than just the plummeting share price. First, the costs. So far, the company has spent $3.5bn (£2.3bn) on the disaster. But City analysts are modelling final costs of an eye-watering $30bn.

Then there is BP's future business. The US has already slapped a six-month moratorium on offshore drilling, and BP may yet face a specific ban, possibly for seven years, raising the devastating possibility of being forced to sell out of the US altogether.