The locomotive is 'Duchess of Sutherland' in red LMS livery, hauling a tour to York from Ealing Broadway. The tour uses the Gospel Oak- Barking line before switching to the East Coast Main Line just before Harringay, so it will appear at low speed on the single-track curve by the south end of Harringay station platform 2.
The return leg will be hauled by 'Union of South Africa' but well after dark, and the morning visit will be a bit dark given the time and weather forecast.
[EDIT] Calls at Finsbury Park 2141-2143, so passes Harringay two minutes before. Real Time Trains live times here: https://www.realtimetrains.co.uk/train/U54874/2020-02-15/detailed
(sorry, prev. link didn't work. Currently  running about 30 mins late).
Next steam: Friday 17 April after the rush hour, 'Tornado' on the Great Britain 2020 (a 9-day steam-hauled tour round the island), and Saturday 18 April about 0835, a very rare visit by 'Clan Line', an ex-Southern Railway Pacific design usually seen at Victoria with the Belmond Pullman luxury train.
Hi Gordon T (or anyone) is there a time or Realtime Trains link for Union of SA this evening?
There is now - see [EDIT] above. Calls at Finsbury Park at 2141.
This morning's visitor, in the gloom. A bit impressionistic (alright, slightly fuzzy). A louder, sharper exhaust sound than usual.
The steam showing at rail level by the driving wheels shows the driver was applying sand to the rails to improve adhesion. Understandable given a wet rail, the climb up from the Gospel Oak- Barking line and the extra drag caused by the train traversing the sharp curve. The diesel at the rear was just idling, providing electrical power for the train carriages.
Shot!!! She looks in fine form, despite being a long way from her home metals!
Steam Watchers - a minute footnote in the current health, social and economic hurricane - all steam-hauled trains local to Harringay are postponed. Summary here.