Spitfire Crash Site: Craig Y Llyn (Mynydd Pen-Y-Cae) Location : Mynydd Pen-Y-Cae, South of Cwmgwrach, Glamorgan, UK. Departure airport: RAF Llandow, Glamorgan Destination airport: RAF Llandow, Glamorgan Phase: On route Nature: Training
Narrative:Spitfire R7057 was assigned to 53 OTU RAF Llandow on 3rd February 1941. While on exercise it flew into Mynydd Pen-y-Cae, South of Cwmgwrach, near Glynneath in low cloud on 12th August 1941. Aircraft impacted at 1,960 feet/597 metres above sea level. Pilot P/O C.J. Day was killed 
Crew: Pilot Officer Colin James Day (Pilot) (Service Number 102080) - killed. Buried Reading (Henley Road) Cemetery, Reading, Berkshire 
Some sources state that Spitfire R7057 was a "presentation" aircraft, bought with public funds and subscriptions to War Bonds, and thus named "CAITHNESS" (see link). The impact site for this aircraft is rather small. Its close proximity to an active forestry track may explain this. Closer examination of the track showed numerous small fragments of melted alloy, spreading approximately 10 metres either side of the impact site. Small piles of wreckage had been collected and a shrine type structure constructed from stones is present.
A party of locals, Leighton Collins grandfather being one, formed a search party to find the aircraft when it crashed.It is thought that the pilots body and parts of the plane were stored in wooden boxes in the Dunraven Arms until being collected by the military.Most of the plane was sunken into the marsh.
Sources:
Link to the website: https://aviation-safety.net/wikibase/150559