While the majority of passenger traffic at Holborn Viaduct was via multiple units, but between 1935 until the finalisation of the Kent Coast electrification scheme and the end of steam a number of semi-fast passenger services to the coast operated. Due to the axle-loading limitations of Holborn Viaduct (not least that the services with the antithesis of prestigious!) the locomotives used on these services and the pure parcels/newspaper traffic were previously top-link SE&CR passenger locos of Wainright's era such as the E1's,  D1's - as well as the more workaday O1's and C-classes.

C-class on a cross-london freight at Holborn Viaduct Low Level

Not sure on this one, but looks like a D1-class to me!

Though I appreciate it's hard to see, there's a C-class on Platform 1, just above the left hand Metropolitan extension tracks

Another D1 after dropping off a mid-morning Parcels train into P2 in 1958. Without a runaround on P2 it seems a shunting move via the runaround in P3/4 would have been required, backing towards Ludgate Hill.

ex-Wainright E1 No. 31507  on a Ramsgate to Holborn Viaduct service in 1961

Yet another D1, this time in 1960 with a mixed passenger-parcels consist from Ramsgate that continued until the line was electrified, albeit transitioning to the BR Standard 2MT's.