Vortex Ring was involved IIRC
I thought something else was involved but I will ask M... T.... next month when he's pi###d.
Edited to add.
I eventually went to Wastelands at Weston Super Mare to pick up XW 216, complete with a brand new lower airframe assembly, and flew it back to Odiham. The F700 hadn't been completed since it acceptance in Aldergrove so I wrote in the post flight section.
'Severe vibration on landing but it cleared on the next flight.'