The song that is playing on the radio when Del Boy and Rodney visit Sid's cafe is Del's favourite song, "Old Shep". In "Diamonds Are for Heather (1982)", Del pays for the song to be played in The Nag's Head, and after being dumped by Heather, he pays a group of carol singers to sing it to cheer himself up.
First appearance of Sid.
'Bertie' Smalls, aka Louis Payne Smalls, was a 'supergrass'. His testimony resulted in the conviction of dozens of criminals, including the infamous Kray twins.
Although there have always been informers, Bertie Smalls was the first to provide testimony and evidence against so many former associates and strike a deal that gave him immunity from prosecution.