How many troops did the Roman Emperor Claudius use to conquer Britain?

The general Aulus Plautius who led the invasion went to Britain with four legions. The Roman legions had 5000 men when at full strength. Therefore, there probably were about 25,000 legionaries. The Romans usually also deployed auxiliary troops of the same size as the legions. Therefore, Aulus Plautius probably had around 50,000 men. Auxiliary troops were forces of non-Romans who supported the Roman legions.
In 43 AD the Emperor Claudius put together four legions. These legions were accompanied by auxiliary troops. In total, Claudius had mustered about 40,000 men for the invasion.