Hard to say Zoe. I would suggest you get a decent builder or a surveyor to advise you. My sister had subsidence on her back wall and it was rather like this on her brick wall.

I agree with Sonia that it probably needs a builder to look. I think they will likely conclude it’s minor- your next step is either cosmetic repair or watchful waiting to see if it’s still moving or a historic thing.

I would also be looking for possible causes…… look for oversized trees or hedges, faulty drains or evidence of similar problems with neighbours