Tim Roll-Pickering wrote:

For that matter why didn't they just retain the Holborn Viaduct name - it
can't have been because they thought passengers might confuse the station
with a Central Line tube could it?!

Possibly because the Ludgate Hill end opened some time *before* the
Holborn Viaduct end - and anyone who's walked the length of those
platforms in a hurry knows how far apart the two are...