Could there ever be wild tortoises in the UK?

[jimothy]

While I was away on a trip in Devon last week, while walking on Dartmoor and seeing some habitats that looked ideal, with global warming and increasing ambient air temperatures, could a wild population of tortoises ever sustain itself at these latitudes?

Would they ever get enough intensity and duration of sunlight? Would the soil ever be warm enough to incubate eggs and maintain a sustainable population? Would they survive the winters if air temperatures were higher? Would predators (and humans) completely destroy them?