Keeping the ERTMS to a limited number of units is a god send. NR have stated, that if ERTMS is fitted and working correctly, then it must be used at all times. That’s why changing ends at Birmingham international, for example, takes time. You have to wait for the ERTMS to load up, even if you’re using it in level 0 (zero). Shunting round the depots and quick turn around will be much easier and faster now along with all the splitting/attaching at Shrewsbury etc. If you’ve ever been on a 158 and heard the ‘ready to depart’ buzzer but no movement for 2 minutes, you now know why. Even longer if you end up over some grids.