staff in the 4-foot during operating hours

It depends on the type of work being carried out as to whether the power would have been off or not. Most likely would have been on. If it was off, there is a chance it may not power back again.

Some signalling upgrade work was planned to be carried out on the fast lines during daylight off peak hours.

The power can be isolated as necessary.

There's a regular p-way gang that patrol along the north end of the Met, mainly in the mornings and early afternoons, when the light and conditions are best. As a driver, we are trained to look out for them, and as individuals working on live track, they're trained to give themselves ample sighting time. Long and short of it – we give them a toot, they move somewhere safe accordingly and acknowledge, and this satisfies both parties. They generally don't work on the conductor rails – you will find one chap may be carrying a large multi-tool that looks like a spanner, used to tighten up or re-jig things on the p-way. One of the guys will act as a "look out" – you will notice he may carry a horn, which he will use to alert his gang upon the sighting of a train. Generally they will move to a place of safety like the cess upon acknowledging the train, or more often than not, given the track layout, will move to a road that is not occupied by any oncoming traffic to allow them to carry on walking at a safe distance from a passing train.

Chalfont and Latimer is pretty tame now I think about it. You should see it when they're walking along the southbound main somewhere between Moor Park and Northwood during the morning peak, and switching between all four lines!

What's a NIRM ?

Network Incident Response Manager

Since when have DRM's been stripped of most responsibilities ?

It's not correct to say that the DRM has been stripped of most, or even any, responsibilities. The NIRM was created as an additional role. The DRM remains fully licensed and available to manage and assist with incidents, including taking silver control where required. The DRM also carries out incident investigation (which has always taken up most of their time, but tends not to be seen because most of this activity takes place "behind the scenes"), CMS, PGIs, emergency signal operator, fully licensed signal operator (on some lines), emergency train operator, making up numbers on stations, and of course covering DTSM desks when required.