PAT testing stands for Portable Appliance Testing. It's a process commonly carried out in London and elsewhere to ensure the safety of electrical appliances used in various environments, such as offices, shops, factories, and rental properties. During PAT testing, qualified electricians or technicians inspect and test electrical appliances for potential faults or defects that could lead to electric shocks or fires.

In London, PAT testing is essential due to the high density of commercial and residential properties and strict safety regulations. Landlords, employers, and property managers must often have their electrical appliances tested regularly to comply with safety standards and regulations.

The process typically involves visual inspections and electrical tests using specialized equipment to check for issues like insulation resistance, earth continuity, and polarity. Once the testing is complete, appliances are labelled to indicate their safety status, ensuring that they meet safety standards and regulations in London.

In London, electrical appliances should generally be tested regularly to ensure safety. A standard recommendation is to perform Portable Appliance Testing (PAT) annually for most appliances in commercial settings.

However, the frequency may vary depending on factors such as the type of appliance, its usage, and the environment in which it operates. It's best to consult with a qualified electrician or follow the guidelines provided by regulatory authorities for specific testing intervals tailored to your situation.