This is a Significant Operational milestone.
The Thrust Measuring Rig (TMR) was an experimental craft designed to provide test data for jet-lift powered VTOL flight. This was a significant step in the development of VTOL flight in the United Kingdom. The vehicle was piloted by Captain Ron T. Shepherd, chief test pilot for Rolls-Royce. The vehicle had previously carried out a first tethered flight on Jul 03, 1953.
Source: "The Flying Bedstead" Thrust-Measuring Rig (TMR) Experimental Research VTOL", Erasmo Piñero Jr., 2018 VFS History Calendar, August