The Regulation of Investigatory Powers Act 2000 in general prohibits interception of communications by a third party, with exceptions related to government agencies. A recording made by one party to a phone call or e-mail without notifying the other is not prohibited provided that the recording is for their own use; recording without notification is prohibited where some of the contents of the communication--a phone conversation or an e-mail--are made available to a third party. Businesses may record with the knowledge of their employees, but without notifying the other party, to

is it legal to record personal phone calls uk?
yes