That would depend on the type of surveillance, the severity of the incident being investigated and the particulars in their contract of employment. Where electronic monitoring and overt surveillance such as email monitoring and CCTV are put in effect permanently, or over a long period, the employer must declare this to any employees affected. The usual process would be for an employer to disclose to the employee that they are going to launch an investigation into their behaviour, this is usually done in a disciplinary setting within the business, the employer may have this written into their company policy and contract of employment to set out criteria which may trigger an investigation and types of investigative techniques they may use. For the fair procedure, if an employer feels that the employee’s behaviour amounts to gross and serious misconduct or is criminal and that informing them of the investigation may hinder the opportunity to gather evidence of their conduct, they may have grounds to conduct covert surveillance without informing the employee.