On Wednesday, 19 July 2017 10:22:17 UTC+1, wrote:
The storm that passed over the London area last night had more cloud to cloud
lightning , in fact more lightning full stop, than I've ever seen before in
this country. There was probably on average 1 bolt per second but strangely
almost no cloud to ground lightning. Was there something unusual about this
storm?

--
Spud

It was a middle-level storm, as explained by Stephen. The resulting c-c discharges always seen to give more light than c-g strokes but less sound. I'd put this display (for c-c lightning)second after 12-13 June 1964 which almost turned night into day and completely obliterated reception on Long Wave.
If there is a c-g discharge from one of these storms it can be a big one. One learns that not all lightning flashes are equal and the one that struck on the morning of 28 Aug 1958 was a monster. A blinding flash, a simultaneous thunderous bang, I thought it had struck the front garden. Not a bit of it; it was 150 yd away, knocked a heavy branch off a large tree and "bounced across the road" according to witnesses. The tree was later cut down.

Tudor Hughes, Warlingham, Surrey.