Shares in BP fell by as much as four percent this morning after it warned it was expected to post an impairment of up to $2bn (1.6bn) and was operating under “significantly” lower refining margins. The FTSE 100 oil major, which in April surprised investors with a better-than-expected oil and gas trading performance in the first three months of the year, maintained much of its momentum in the second quarter, but said that “onerous contract provisions” meant it was setting aside up between between $1bn (£780m) and $2bn…
