It would be a little misguided to describe it as one of European football’s worst-kept secrets. Because a club still giddy off the celebrations of their first league title win in six years never once hid their desire to sign the former Rangers ace this summer. And, on Friday afternoon, they did exactly that. 12 month after his spell at Rangers was brought to an end – albeit thanks to factors beyond his control – a youngster who made quite the impression at Ibrox became one of the most expensive signings in the history of a club with a European Cup title in their trophy cabinet. And, in truth, …