Having a read through, I thought I would share my experiences travelling to Euston over the past few of years. I've only been a handful of times with Virgin. The first time was back in 2013, we arrived from Lime Street, saw a number of staff "checking tickets" at the end of the platform so had ours ready only to be grunted at and waved through without it being glanced at.
The return leg of this journey was the following evening however didn't have a ticket check before boarding. As it happens we were on the wrong train anyway - tickets were booked for the lets say 1823 Liverpool train (I cant remember the exact times), we boarded the 1821 and didn't think anything of it until I realised there was another Lime Street train 2 minutes apartwith different calling points and we were booked on the other! As it happens, nobody checked the ticket before boarding, on board, or at Lime Street.
I have been between Liverpool and Euston twice since then with Virgin trains , the first time had no ticket checks at any point on either the outbound or return journeys, and the 2nd time which was only in October of this year, again had no ticket checks outbound and only one check on the return, which was mid journey by a very polite chap.
Although not Virgin, going back many years I went to Euston changing at Crewe on London Midland with their £10 great escape ticket (which I really miss!). Again of the 2 trains out and 2 return, only had the tickets checked on the 2nd leg of my return journey - no platform checks!
I was quite shocked at how slack the gateline was at Euston, maybe I just travel at the right time of day or something but out of the 6 or so times ive been, Ive not had it checked at Euston itself on any occasion.