Note: The above caterpillar was photographed in Britain.

Although your caterpillar has very distinctive markings, the species are difficult to identify in many cases. Depending on what the cat has been eating, colors and patterns can vary a lot.

Also, caterpillars moult several times and yours might not be the final moult, that can affect the appearance greatly.

Yours does bear a resemblance to Acronicta rumicis, the knot grass moth, this does occur in England. Search for online images and see what you think. Over here, moths in this genus are called Dagger Moths.

A beautiful caterpillar. A beautiful photo.