Immigration enforcement officers visited Roosters Piri Piri on Cambridge Street at around 2.30pm on Monday, where they carried out checks on staff working there, the Home Office said today (Wednesday).
A 21-year-old Pakistani man was arrested after he was found to have over-stayed his visa.
He has been detained pending his removal from the UK.
The Home Office said bosses at Piri Piri will have to provide proof that the correct right-to-work checks were carried out on the man or they will be fined up to £10,000 for employing him.
Chief immigration officer James Masters, from the Home Office’s Thames Valley Immigration Enforcement Team, said: “Our officers are out almost every day carrying out these kinds of operations, and where we find someone who is in the UK illegally we will seek to remove them.
“I also hope this operation sends out a message to businesses – you must carry out the correct checks on your staff or you could end up with a heavy fine.”