Yes Ksimboy, There was actually two drops around the same time. One in the US on Purple Star and one South Cerney or perhaps Keevil. both with CVRT. The UK drop may have been a rehursal!
My friends at JATE had been working on some new side frames for the HSP unfortunatly the design had not considered the wash away to handle tip off. A rather expensive modification was proposed. It was shelved as not affordable. The round poles were kicking around for ages being used as rollers to get MSP CoG.
We subsequently tried to bring it back to life around 2004/5 for an updated version of the CVRT that was heavier. Only to find the existing frames were also outside the envolope. HSP may have been on the A400M Exhibit A list. It may be that someone wanted to drop it to justify it being on the list for A400M.
You could not make it up! That was the icing on the cake and consigned one of the reamining two HSPs to the Airborne Museum at Duxford. I hope they look after it as it took the efforts of many Army folks to get it there.