Why did the Romans leave Britain and what lead to the downfall of the mighty rom

Question:

Why did the Romans leave Britain and what lead to the downfall of the mighty roman empire?

Additional Details

5 days ago
so what happened to rome after that?

5 days ago
with respect, i havent been to a library re this subject matter as i was asking purely out of interest and not for any academic purpose. my subject matter is criminology, not history, and the question was asked purely on the basis of me catching the last half an hour of 'Rome' on UKTV History earlier this evening!!!

5 days ago
thanks guys! xxx

Best Answer - Chosen by Asker: 5 days ago
so what happened to rome after that?