owl in se23 (london)?! or fox?

Hi all Brand new to this forum - I hope someone can help me with this! Every night for the past 2 weeks or so just after dusk I've heard a call that sounds like it *could* - *could*! - be an owl. I live close to the Garthorne Nature Reserve in SE23 but not close enough that I'd expect to hear one. Anyway I managed to record it this evening. It sounds big so I don't think it's a songbird and it doesn't sound like a dog or a cat, or anything small like a squirrel. It might - might - be a fox, but I don't know. I've never heard a fox make this noise in London in over 25 years here. I've uploaded it here:
Voice 012_003.m4a