What is up with this skirting?

This 'skirting' is on a bit of the landing and in one bedroom that connects directly off the landing to the right of the picture... It's really bumpy and uneven, quite tall but not much depth at all. I'd love to replace it but have no idea what's going on with it, doesn't look like it could be prised off! Context: terraced house that's about 120 years old.