I guess the very mention of the word 'rat' will give the creeps to many people let alone this photo of one! Ever since "The Plague" of 1665 we Brits have hated the rat, albeit that the plague was brought here by the black or ship rat, not the common or brown rat (Rattus norvegicus) shown above. It's a shame these creatures are so vilified in many ways as they are actually quite cute, extremely adaptable and very intelligent. At that point my defence of them has to stop as I acknowledge that they are a nuisance and do spread disease.
The origins of the brown rat are unknown but it is thought they came from Asia, spread across Europe and actually came to Britain via ships coming from Norway around about 1730 when the Hanoverian kings ascended to the throne. (My book does not explain the connection).
It is the brown rat that is by far the most common with the black rat confined to some ports around the country where they have come in with the cargo on ships. The brown rat is widespread and it is found almost everywhere and despite expensive and extensive attempts to poison it out of existence its fertility rate means that it recovers and spreads very quickly. Quite often we are oblivious to their presence as they are very shy and largely nocturnal. They are omnivorous but their preference is for grain and so garden bird feeding stations is a favourite feeding place for them too.
There could be rats in your garden you don't know about!