Right so I had almost the exact same thing happen to me in 2019, back garden in Brum, except mine was more like a dragging sound than footsteps - slow, deliberate, completely rhythmic. Set up a recorder on the chimney stack the next night fully expecting to catch a fox or something and got absolutely nothing on audio, which if anything is weirder than catching something.
The thing people always miss is the weight distribution. Animals skitter, they shift around, they're unpredictable. What you're describing sounds like it has intent and that's the bit that keeps me up at night if I'm honest. Got any recordings? Even a phone voice memo from the moment would be worth analysing, there are free spectral analysis tools online that can pick up frequencies you'd never catch with your ears. Drop it in here if you've got something, this community is pretty decent at pulling details out of audio.
