I've seen on Twitter (spread over a string of messages) that for 4 nights a week a Class 710 is running 300 miles (two trips a night up the WCML to Tring / Milton Keynes Central) and if / when a train has made 7 successful fault-free such trips then it will have passed the Network Rail test requirement and be accepted for the start of staff training.
Its going to be a very tight timeframe but maybe, just maybe, at least one train will be ready to enter service next week?
https://twitter.com/cmpd_date/status/1087067773510053889
edit to add: what I am not understanding is how a few high speed runs can thoroughly test a train which will spend its life travelling at lowish speed (40mph and less) stopping at stations every few minutes... doors open / close and all that!