Strange knocking coming from inside my walls every night at 3am

Right, before jumping to poltergeist conclusions there's a few mundane things worth ruling out first. Thermal expansion in pipes and joists is massively underrated as a source of rhythmic knocking, and it often peaks in the early hours when the heating drops. 3am is a classic time for this because thats when indoor temperatures hit their lowest point overnight.

That said, the regularity you're describing is interesting. Random thermal movement doesn't usually hit the same time every night with any consistency. If it genuinely locks onto 3am with precision, that's worth documenting properly. Get a voice recorder running and note the exact timestamps over a week or two.

A few questions - which wall is it? External or internal? And does it correlate with any change in weather or temperature outside? Also worth checking whether anyone else in the household hears it or if it seems to be just you. That detail matters a lot in terms of how we interpret what's happening. Would love to hear more specifics from you.

@MoonlitNight makes a fair point on the thermal stuff, but 3am specifically is worth noting. Pipes expand and contract with heating cycles, usually tied to when your boiler kicks in or shuts off, so that tends to follow a pattern you can cross-reference with your thermostat schedule.

What makes poltergeist cases stand out in the literature is when the knocking responds to stimuli - ask it to knock twice and it does, that sort of thing. If its just the same rhythm on a loop regardless of what you do, thermal or a pest is far more likely. Squirrels and rats in cavity walls are genuinely common in older Yorkshire properties and they go quiet during the day.

Try ruling out the building explanation first then documenting whatever's left. That's how you build a case worth taking seriously.