.... not sure if it's worth a listen, but on Radio 4 (BBC) tomorrow
(Tuesday/1st), there is the following:-

" 1 July 2008
John Tusa looks back at the events making the news 40 years ago. Red
rain falls over much of Britain. "

http://www.bbc.co.uk/radio4/1968/

[ only 4 mins so no depth! ]

On the 1st July, 1968, 'coloured rain' was reported across much of
England and Wales, from mid-level Ac cas, and associated with some
'interesting' weather! Hailstones were recorded with a diameter up to
7 cm at Cardiff/Rhoose and according to TORRO, this was part of a
series of only 10 or so 'widespread large hail' events in their
catalogue. Counties affected stretched from Cornwall, Somerset and
Devon to South and West Yorkshire. Other areas reported 'severe
thunderstorms', large hail, torrential rain and 'day darkness' and
deaths due to lightning strikes. The 2nd of July, 1968 also
experienced some torrential rainfall with flooding in SW England.

Martin.

--
Martin Rowley
West Moors, East Dorset (UK): 17m (56ft) amsl
Lat: 50.82N Long: 01.88W
NGR: SU 082 023