Trainline have sent me an email advising that "To celebrate
Virgin Trains' 20th Anniversary, over a million seats are
available on all West Coast routes for the entire summer."

Available second class fares include £4.00 Euston to Nuneaton,
£10.00 London to Manchester and £14.00 London to Glasgow.

According to Trainline, the only stipulation is that you have to
book by 14/3/2017.