our café nero manageress has tadpoles in her pond and this is a regular event.
universities of Edinburgh and Glasgow have researched this and the summary is:

“Reports increasingly point towards tadpoles surviving through winter in their ponds and becoming frogs the following spring. Our findings suggest that temperature and food are not the primary causes, and that tadpoles delaying metamorphosis have a double advantage of being more developed and arriving sooner than that year’s tadpoles.”

https://www.ed.ac.uk/news/2015/tadpolesurvival-261015

Thanks, some of them have legs and there are some that are tiny frogs, thanks for reply.

Amazing!