Convolvulus Hawkmoth

I was at RSPB Minsmere last week, mainly posing for photos for Bird Watching magazine, but also doing a spot of birding. However, perhaps the highlight of the day was this whopper of a caterpillar rumbling along one of the paths. I believe it is a Convolvulus Hawkmoth, which is quite a scarce migrant moth. Caterpillars of this species seem to be variable in colour. But the spots and red 'tail spike' I think point to this moth.