What is this please?

[pencilcaseandcabbage]

Can anyone tell me what this plant is? It was left behind by previous owners. Thank you!

Does it have any smell, for instance if you crush the leaves? Has it flowered at all?
It's hard to tell from your photo, but maybe salvia microphilla? The leaves have quite a strong smell.

Or thyme? Again, the leaves would smell strong. (And v.nice)

No smell, sadly, and I don't think I've ever seen it flower. It's been in a corner that doesn't get any sun. I've added another close up of the leaves, in case it helps.

I think it’s a Spiraea

I also think it is a spirea

Another vote for Spirea.

Doesn't look like a spirea to me. It looks like some form of salvia.

Yes, I think it is spiraea arguta. It looks like it needs some tlc and some fertiliser.

Ordinary Growmore granules are cheap and so is tomato feed, either would be fine.

I agree Spiraera, you probably won’t get flowers this year, so alight trim to give it a less leggy appearance perhaps.
I’d also take it out of its pot, shake off the old compost and repot it with new compost. Then feed it.

Azalea?

Thank you all. I've had a look at pictures of spiraea online, and the ones I have found, the edges of the leaves are jagged rather than smooth. But I'll give it some feed and a bit of sun (the spot where it was never got any) and see how it does. What should I be trimming? A bit off all over? Cutting out any bits that seem more 'dead'? I don't really know what 'leggy' means. I've never been a gardener (as you can no doubt tell 😂), but we have an extremely bare patio atm, so it will be good to see if I can keep it alive, at least.

I would cut out anything that is dead right to soil level. It should be obvious now as these stems won't have leaves. Worth refreshing some of the compost and adding feed such as Osmocote. I wouldn't prune now ( other than removing dead) as you may cut of flower buds and will be easier to identify with flowers.

‘Leggy’ means long stems that tend to have only a few leaves at the end. The plant often struggles to send moisture up to the leaves at the ends. I would prune those and the apparent dead ones by a couple of centimetres to encourage sprouting from lower down on the stem and the base of the plant.
Just my opinion, but I respect the opinions already expressed.