The Victoria line was built with interchange in mind. All but one of the 16 stations link to another line, or maybe several, making ease of transfer the priority. But just how long do those connections take? I've worked my way down the line with a stopwatch to find out.
n.b. I only walked these one way (walking the other way might be different). I walked from platform to platform (apart from at mainline termini). I timed from the moment I left one platform to the moment I arrived on the other. I walked to the nearest platform, which may not be the platform you need. I did this experiment off-peak. I always walked down escalators, but never up. I walk quite fast. I am not sad, honest.
Walthamstow Central (Greater Anglia → Victoria) [1m10s] The original route down to the Victoria line is direct from National Rail platform 2 (although now there's another entrance direct from the bus station). Head down the steps, through the ticket barriers and down the escalator. If arriving here by tube, it's quickest to sit at the front of the train.
Blackhorse Road (Overground → Victoria) [1m20s] Up to the cheap-looking footbridge, follow the passage into the ticket hall, then double back and head down the escalator.
Tottenham Hale (Greater Anglia → Victoria) [1m15s] It's dead easy to step up to the ticket hall from the northbound National Rail platform (but a rather longer up and over from the southbound). There's a nice row of plants above the escalators.
Seven Sisters (Victoria → Greater Anglia) [2m30s] To interchange here, best sit at the Brixton end of the train. Exit is via a twisting passage with two-way flow, full of awkward blind spots. Then double back in the ticket hall and follow a straight passage to the National Rail platforms. Think functional, not beautiful.
Finsbury Park (Victoria → Piccadilly) [5s] Fabulously swift passage to parallel platform. Thank you, Victoria line designers. Finsbury Park (Victoria → First Capital Connect) [1m10s] Woo, spiral staircase! 50-or-so steps lead up to a grim passage below the National Rail platforms.
Highbury & Islington (Victoria → Overground) [2m25s] A slower than usual yomp, because they're refurbishing an escalator at the moment, but it's never quick. A lot of up and down is involved. Highbury & Islington (Victoria → First Capital Connect) [5s] A simple short passage across to the gloomy Moorgate-bound platform.
King's Cross St Pancras Sorry, but this is indeed as complex as you're expecting... (Victoria → Piccadilly) [50s] Don't follow the signs! Take the sneaky staircase accessed from the 'Euston Road' end of the platform. (Victoria → Northern) [1m5s] Ditto. (Circle → Victoria) [1m50s] Not such a bad journey, via the original main escalator link. (Victoria → King's Cross mainline) [4m] That's four minutes if you follow the signs, and trek the evil long route via the new passages and the Northern ticket hall. Worst interchange on the entire list... (Victoria → St Pancras High Speed) [6m] ...apart from this, which is worse... (Victoria → Other St Pancras services) [8m] ...and this, which is godawful. This proves that either a) only mugs follow the official signs or b) St Pancras really is a very long way from the Victoria line.
Euston (Victoria → Northern) [15s] So long as you want the southbound via Bank, dead quick. Not so quick otherwise. Euston (Victoria → Mainline services) [3m] That's from the bowels of the station to the main concourse, probably battling behind lots of slow people with suitcases.
Warren Street (Northern → Victoria) [1m30s] This is the interchange that feels the most old-school, past some lovely cream and black tiles (and via two escalators).
Oxford Circus (Victoria → Bakerloo) [20s] Another splendidly quick parallel platform passage. They designed this line so well, those 1960s planners. Oxford Circus (Victoria → Central) [1m50s] A long trek down a long passage past a busker. Interestingly it's much quicker walking in the opposite direction, from Central to Victoria, which takes only half the time [55s]
Green Park (Victoria → Jubilee) [1m20s] This is the 'quick' interchange at Green Park, via steps and a single escalator. Green Park (Piccadilly → Victoria) [1m40s] This involves a long passage, but it's still a minute shorter than the really long interchange at Green Park, which is (Jubilee → Piccadilly) [2m40s]
Victoria (Victoria → National Rail) [2m] This requires ascent by escalator into a hellish ticket hall filled with milling tourists, then further steps up to reach the mainline concourse. Victoria (Circle → Victoria) [1m10s] A fairly quick descent, so long as you're at the right end of the platform.
Pimlico There is no interchange here.
Vauxhall (Victoria → South West Trains) [3m10s] A long escalator, a long passage, and then entry into the back of the station where there appears to be absolutely no guidance as to what mainline trains are leaving when from which platforms. A poor experience.
Stockwell (Victoria → Northern) [8s] That's the fifth brilliant connection to an adjacent platform. I say again, the Victoria line was designed with interchange in mind. Don't expect anything anywhere near as good from Crossrail.
Brixton (Victoria → Southeastern) [4m] Riding up the escalator, then walking up the steps into Brixton, takes 1m40s. There are then no signs pointing towards the National Rail station concealed round the corner, which is atrocious signage (unless I missed something) (I don't think I missed anything).