Apple admitted in March that it had been in takeover talks with the Hertfordshire-headquartered company, in which it has an 8.3% stake, before deciding against making an offer. Analysts immediately suggested Tsinghua’s move could force America’s biggest company to come back to the table and caused Imagination shares — which were relegated from the FTSE 250 last year — to jump 20.5p, or 14%, to 171.5p.