The long-running takeover saga surrounding iSoft, the software company involved in the £12bn project to upgrade the National Health Service IT system, took another dramatic twist on Friday with an unexpected £160m all-cash bid from CompuGroup, a German medical sofware company.

The agreed offer values each iSoft share at 66p and trumped an earlier all-share 52.7p offer from IBA, an Australian software company, that valued the UK software group at £122.5m.