I came across this boxing venue looking up some things on the internet about Welsh heavyweight Jack Petersen. Wanted to share info on it to add to your venue data base if you don't have. I didn't have it.
Holborn Stadium
Holborn, London
85 High Holborn, England
Gave it site rating of 1 use what you think
Seating Capacity: 700 was noted in wiki site when it started it's existence in the late 1800s.
Good Website on it:
https://en.wikipedia.org/wiki/Holborn_Theatre
Started out life as the New Royal Ampitheatre as an equestian ring and theatre in 1867 and operating as such till 1886. It went through several name changes becoming the Holborn Theatre in 1884. The theatre was 76 ft wide x 130 ft in length and housed about 700 people. The venue ceased to perform live theatre in 1886. It became eventually Holborn Stadium and later to become called The Stadium Club featuring boxing matches through the early 1900s through till it was closed and eventually demolished in 1939. (Reference website the.hitchcock.zone/wiki/Holborn_Stadium_Holborn_London).
In 1929, the National Sporting Club was forced to close it's premises at that time in Covent Garden and for a while moved into The Stadium Club, Holborn. NSC moved on to 21 Soho Square in January 1930.
Some fight card announcements in various newspapers looked at from 1917-1919 describe it, Holborn Stadium, High Holborn, W.C., One minute's walk from Chancery-lane, Holborn and Museum Station, Nearly Opposite Holborn Empire
Could not find any outside photos of it. One posted here of a boxing match going on inside in 1905 is on the wiki site.