The 24-year-old has successfully replaced Alberto Moreno at left-back and nailed down a starting place this season.
It has been a long journey for Robertson to reach this level, having been released by Celtic as a 15-year-old, which forced him to work his way back to the top through spells at Queens Park, Dundee United and Hull.
Celtic chief executive Peter Lawwell might well wince over the knowledge that the left-back is now worth nearly £38.7m, according to CIES Football Observatory.
The defender is nowhere near the peak of his powers yet, but on the evidence of this season it looks like Liverpool will have an outstanding player for the foreseeable future.
You can’t direct much criticism at Celtic for letting him go, however, because a lot of clubs have unwittingly released players who went on to have very good careers elsewhere.
Nevertheless, it has to be considered a mammoth mistake and one which might haunt the Scottish champions if and when his valuation surges.