Except the times you are quoting from @Uter are Brighton to City Thameslink, not LB. The equivalent station in 1912 would be Holborn Viaduct; how long did it take to get there and how many changes? Yes the May 2018 service to LB will only be a few mins quicker at 1hr 02 for a fast peak service but four 12 carriage trains an hour carrying thousands more passengers. Curse these damn facts.
1912 times are Brighton to LB direct - the 8:15 one stop at East Croydon, the 8:45 non-stop. Holborn Viaduct was a SECR station, not the LBSC.