IIRC, an 'Accompanied Letdown' is still an annual requirement for VC10 training purposes. The manouevre is designed to allow a tanker to lead a receiver to the runway when the receiver has suffered degradation of it's flight instruments for any reason. It's challenging to find a fast jet willing to accommodate the training requirement as it takes more time than they generally have available for things other than their own requirements. Consequently it is common practice for two tankers (especially 2 VC10s) to fly the fromation, which terminates at specified minimums above the runway. The procedure was incorporated into ATP56(B) from, I believe, UK AARNIs, and is now accepted practice worldwide. I think the RAF is the only Air Force to have the annual training requirement though.
It is fun and it does look good too, but when used for real, when it's snowing, with half a mile visibility and a 400ft cloud base, the wingman is a single-seat fast jet with only his secondary flight instruments availabe and it's dark - all the practice is worthwhile.