Link progression by seniority, and thus by age, was normal, all the way up to the top as a fireman, and then starting again upwards as a driver. The pay structure also rose in a similar way. There were a few, however, who either by their own choice or that of management, got taken off the high speed and arduous turns as they approached retirement, dropping back to local services. Nine Elms did have many express turns, but of course a lot of depots, even nearby Feltham, did not. There was a minor LNER branch shed which closed in the 1930s, the crew were offered relocation anywhere, one driver chose a vacancy at Kings Cross in London, and purely by their long serving seniority pottering up and down the rural branch were straight into Top Link main line expresses.
Lord Hawke was at Nine Elms in 1939 as well. Pre-WW2 the "Nelsons" were divided pretty equally between Nine Elms and Stewarts Lane (actually walking distance apart, in Battersea), as the latter covered services like the Dover boat trains as well, but once the Bulleid Pacifics came along they were concentrated on the Waterloo to Bournemouth line. It was number 860 until 1948, only changing to 30860 with nationalisation. The Southampton boat trains were pretty random, dependent on shipping schedules, some days none at all, others the running department were scrambling all over for locos, carriages and crews, which cascaded down to what was available for the scheduled expresses on any day.