Stage appearances by Marvin, Welch and Farrar, and latterly by Marvin and Farrar, resulted in demands for 'old' Shadows numbers such as FBI and Apache etc. So in 1973, Marvin and Welch bowed to the inevitable and announced that the Shadows would come together once or twice a year for recording purposes only.
The performances of Marvin, Welch, and Farrar, and later just Marvin and Farrar, led to fans requesting the return of classic Shadows numbers like FBI and Apache.  In 1973, Marvin and Welch decided to record together only occasionally for the sake of their fans.