1942 Herefordshire TRE Halifax crash

The 1942 Herefordshire TRE Halifax crash occurred on 7 June 1942 during World War II, in the south of Herefordshire a few miles east of the England-Wales border. The Royal Air Force operated Handley Page Halifax II crashed killing eleven people and several important British radar scientists. It is the UK’s worst ever military test flight accident.
Investigators determined that improper engine maintenance/assembly procedures caused the accident.
History.
Accident.
The aircraft involved was Handley Page Halifax II "V9977" from the Telecommunications Flying Unit (TFU). The aircraft had taken off from RAF Defford, to which it was intending to return; RAF Defford was the home of Britain's research on radar, and the Telecommunications Research Establishment (TRE) had recently moved there in May 1942. The accident occurred at 4.15pm on Sunday 7 June 1942. The aircraft was carrying a secret cavity magnetron, as part of a prototype H2S centimetric radar undergoing trials.
The crash was on the Courtfield estate, in the parish of Welsh Bicknor. The site today is a few metres north of Herefordshire-Gloucestershire boundary, north of the B4234; the Wye Valley Walk passes close by.
Cause.
A fire had started in the outer starboard Rolls-Royce Merlin engine, which had spread to fuel tanks in the wing. The pilot had tried to make an evasive landing on flat ground next to the River Wye, but before he had time to do so, the wing structure burned through and the starboard wing severed. The Halifax aircraft then dived five hundred feet to the ground.
After an RAF investigation, it was found that the crash was caused by a tappet valve nut being improperly tightened.
Victims.
Seven RAF personnel were killed plus Alan Blumlein and three other radar scientists.
Memorial.
A memorial was built next to the site, with a memorial service on 10 June 2019; the memorial was mostly due to an employee of the "Hereford Times", with help from the EMI Archive Trust.