I hope to goodness this is the same incident as reported by chocodoodloo yesterday evening, the current BBC report cites the Air Ambulance being involved which seems consistent as does it being on the Westbound carriageway.
https://www.bbc.co.uk/news/uk-england-wiltshire-45744235
https://www.thisiswiltshire.co.uk/news/16960788.man-died-when-morgan-sports-car-crashed-on-m4/

Very sad to read.

2009 4/4 Sport Henrietta
1999 Indigo Blue +8
2009 4/4 Sport Green prev
1993 Con Green +8 prev