Certainly not on these facts, held the EAT in City and County of Swansea v Gayle.
Mr Gayle was dismissed after his employer covertly obtained video evidence showing him, on five occasions, at a sports centre while he was being paid to work.
Noting that the video evidence was taken in a public place of somebody in a public place (outside the sports centre), the EAT held that fraudsters can have no reasonable expectation that their conduct is entitled to privacy. When the employee was on his employer's time, he had no reasonable expectation that he could keep private from his employer where he was or what he was doing.
The EAT also pointed out that only if faults in the investigation are relevant to the dismissal is it likely to be held unreasonable. Even if the dismissal was already sufficiently evidenced before the covert surveillance, the employment tribunal was wrong to find unfair dismissal based on the covert surveillance: at most, the video evidence was irrelevant to the dismissal. An unnecessarily thorough investigation is unlikely without more to make a dismissal unfair.