That would probably be a Blackmail offence, the intent requirement is about gain (to you) or loss (to the other party) and there's a bunch of Reasonableness invocations because it depends whether the prosecutor can make out that a Reasonable person should know they aren't entitled to ask that you do this to get your property back, as of course one can gain (or the other party may lose) in a reasonable transaction.

For example I once left a laptop on a train when travelling to my mother's house for Xmas. At the time my mother still lived where I grew up, at the edge of Metro-land, and so of course most people on that train wouldn't steal a laptop, they probably earn more than the laptop was worth in a day's work. But I stepped off the train with my other belongings, realised as I walked away and it's too late. The train operating company is under no obligation to like, stop the train and bring back my laptop right? It's unfortunate, but it's not on purpose. A week later I picked it up from their main hub. Their behaviour was entirely reasonable.

If you're thinking that this rule about theft means some crimes aren't theft then yeah, the most notable example in English culture is the crime of "joyriding" which is when you take somebody's car and you drive that around for a while and then you just get out and run off. That's not theft because, as we saw, no intent permanently to deprive (because it destroys evidence like fingerprints some joyriders might torch the car, but that would be intent permanently to deprive). So the crime of "Taking Without Owner's Consent" or TWOC was invented for cars and there's a fun rabbit hole you can disappear down as crooks take like boats and other things and the exact wording of that law is interpreted by courts as to whether it's TWOC if you took a bicycle, or a rowboat, or...