Car insurance is a legal requirement if you intend to drive on UK roads, and with the Police having number plate recognition cameras, it makes it super easy for them to know whether a car is insured or not.
If you are caught driving without car insurance, you should expect hefty penalties, with the minimum being a £300 fixed penalty with 6 points added to your licence. For more serious cases handled in court, penalties can include unlimited fines, disqualification from driving, seizure of the vehicle, possible destruction of the vehicle, and most likely higher car insurance premiums for the future.