What makes a good verification tester?

Sounds impressive of course but as we know 10,000 connections is small beer in many ways and the signal department has always managed to manually check hundreds of things at hundreds of sites when anything potentially dangerous is discovered. In that regard nothing really changed when signalling installation and maintenance was outsourced as the separate companies remained closely tied to one another and to LUL.

Of course some wiring errors are not discovered for years despite routine operation, functional testing and maintenance. One case that I recall occurred at South Harrow during a colleague's IRSE Signalling Tester assessment where a wiring error on a relay top that had existed for years was discovered during the signal selection proving.

It is of course bad when an error becomes apparent immediately following an otherwise successful changeover. Wood Green stage 1 in the late1970s was such an example. It was Sunday morning, the changeover was done and dusted but there were problems with the electronic TD which was relatively new at the time (having been on trial at Earls Court) so most of the 100+ staff on site had returned to depot but a few of us remained assisting our supervisors and the TD lineman. The first reverser came in ran into the siding leaving the points tracklocked and following trains beginning to be queued in the northbound tunnel within a fairly short while. The Chief installation supervisor was still on site, as was the DO Tester, and went to investigate, the upshot was that F&G tracks had been reversed somehow sometime prior to the changeover. This went unnoticed by the Tester on the changeover but the incident had instant and lasting repercussions for the installation supervisor deemed to be responsible and for the way in which future jobs were undertaken. My recollection is that Wood Green was one of the first changeovers I worked on where the outside responses were not done on the night but in advance in the preceding week by night staff while day staff were still doing some wiring in the temporary relay room (which was replacing Wood Green cabin). Interestingly the ticket strip used to temporarily label the 1BA fuse bays had had F & G tracks crossed out and swapped over presumably by the day staff that were installing the track dropping boards in preparation for the changeover but the night signal supervisor was the one formerly disciplined.

I couldn't stress more the need to check everything just as much when routinely replacing a relay or other equipment as when installing anything from new.