David Walliams, Amanda Holden, Alesha Dixon and hosts Ant & Dec joined Cowell at the first day of shooting.
2012 Got Talent winners Ashleigh and Pudsey have gone on to worldwide fame, while other success stories from last year include boyband Loveable Rogues and opera duo Jonathan & Charlotte.
The show is open to acts of any age, background or talent and the panel will visit Cardiff, London, Glasgow, Manchester and Birmingham to find the UK's next big superstar.
There is a still a chance for acts to secure a spot on the ITV series at one final day of Open Auditions with producers at London's Oval on Saturday, January 19.
Britain's Got Talent will return to screens in the spring.