Genuine question, as you were going to hit your oyster cap, why didn't you just buy a paper ticket on arrival at Victoria? (Purely out of interest).
If you get a chance to go again, I'd recommend getting one and then heading out to the further zones. Something like the SouthEastern or SWT Metro lines with loops make it very easy to come back on yourself. I often go round on SE, change at Hither Green, head down to Orpington and back via Bromley. Or at least Denmark Hill and maybe over to Clapham. Either way, its seamless on a paper ticket. Worth doing.
Oh and plenty of people go Victoria to Clapham, mostly for changing. I do when I'm going to and from Raynes Park and want some Electrostar in my life or when I need the area around Victoria.