Apart from the Wokingham storm other candidates (mostly on circumstantial grounds ) for warm
season
type supercells might be the Dover storm ,14 Oct 1964 (Pedgeley,Weather1965 p351 and following
correspondence),the Wiltshire Hailstorm July 1967 (Hardman ,Weather 1968,p404,and the South Coast
Hailstorms June 1983
Add to that the Dunmow (Essex) Hailstorm ,May 1985 (Elsom & Webb,Weather 1987?)),

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regards,
david
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