Astra declined to comment as its shares tumbled 9 per cent, or 1132p, to 11,500p, with analysts questioning whether a tie-up would be achievable – one saying they were ‘perplexed’ by the talks. A tie-up would be one of the sector’s biggest mergers, although the news met with little optimism from industry analysts. A mega-merger would also fuel concerns that Astra could move its main stock market listing to New York, in what would be a hammer blow to the London Stock Exchange. Soriot has increased speculation by striking multi-billion-dollar deals in the US and has previously described Astra as a ‘very American company’. A tie-up would, however, vindicate his decision to reject a £70billion offer from US rival Pfizer in 2014, when Astra was vulnerable to a buyout.