How big is it? Does it have caterpillar type legs or is it more like an earwig?
I can't see it well enough on my tablet to decide but if it's about a centimetre in length, black with yellow markings & kind of mean looking then it's the larval stage of a ladybird, so very much a goodie! A weenie version hatches from the eggs, eats a lot & grows, forms a cocoon in which it morphs into the red adult.
Just check 'ladybird larvae' on Google images to compare.

If the caterpillar is fuzzy, it isn't a ladybird larvae - they have no fuzz or hairy bits at all. Its not possible to magnify the picture to see it clearly, but mostly, dark, hairy caterpillars are moths or butterflies.

Look at the lower pic, it's a ladybird larva. The photos are terrible but it was interrupted in building it's cocoon? It's just a bad camera pic with flash on? & removed from where it laid it's bed.
Even the leaf is a completely different colour in the two images?
For anyone taking these kind of pics, snap at a reasonable distance if you don't have a macro mode on your camera. It's much easier to get a focused shot if you just capture things that are in the range of your camera. Then use software on your device to zoom in or cut the shot down to just include the subject.

Ladybirds don't build cocoons. They form naked pupae on the undersides of leaves or branches when ready, and the adults that hatch either start another generation, when prey are still available, or fly directly to a cool, sheltered place to hibernate until the next season.

I did put a ? after cocoon.

Greenfingers describes it as a 'fuzzy' caterpillar - there's nothing fuzzy about ladybird larvae, they're hairless.

Apologies for the ‘terrible pictures’, I usually don’t post such dreadful photos but it was the best I could get at the time.

I have since discovered that the caterpillar was in fact dead, and it wasn’t a ladybird larvae. The foamy thing the caterpillar was sat on contained a spider.

Oh, and I took better pictures the following day but the site would not let me upload them.