Liverpool have wrapped up their signing of Glen Johnson from Portsmouth. The lingering doubt, though, is how much of a role can arguably Britain’s finest full-back play in transforming Liverpool into Premiership champions.

On last season’s form, Johnson is certainly England’s best full-back. His attacking raids invariably result in finer distribution than, say, Ashley Cole, he’s more Situs Bandarq trustworthy than Micah Richards and probably now edges a fully fit Gary Neville for his country’s No.2 shirt.

Whether he is the best full-back in England, however, is a far more complex debate.

Chelsea must believe so or why would they risk losing Portuguese Jose Bosingwa (who cost £16m from Porto last summer). Meanwhile, it is Arsenal’s Bacary Sagna who this month took steps to deny publicly reported interest from Real.

What’s certain is Johnson appears a more supreme Premier League athlete than Liverpool’s current …