Yeah that's a good point. Did manage to catch one in the end, 1W92 Gatwick Airport to Bedford, from between St Pancras Intl and St Albans. Was a great fun, little slow out of St Pancras but quickly hit the fast lines and started speeding passed all those 319's! Think it was 700004 operating. Great expereince, even for rush hour there were a few spaces on the train, though it was extremely busy. I guess if the other Class 700 diagram trains hadn't had been cancelled, this train probably wouldn't be as packed given it had 12 coaches. But an enjoyable experience overall, nice A/C and very spacious inside, my favourite part being the destination displays which are very informative. To be honest, can't see what all the fuss is about!
The MML is slow through Kentish town up to Carlton Road junction where the ladder takes you from the slow to fast lines. The close signal spacing there prevents faster speeds anyway. The rapid acceleration is through the tunnel and past West Hampstead, or if it stops there, north to Elstree tunnel.
700004 is an 8-car train and I don't think they are running on passenger services yet. Maybe it was 700104. They are good people movers. Once all the early grumbles are out of the way, they will be seen for what they are and ease the heavy overcrowding on the MML. The seats are good enough for the average journey time on the line, (25mins - e.g. St Pancras to Harpenden) so for some actually being able to board their desired train all in the peak will be a blessing. Come October when passenger levels return to normal, the space will be well appreciated.