That's caused by straddling metre-wide speed cushions. What happens is the weight of the car forces the tyres down and outwards on the chamfered edges of the speed cushions. February frost and snow left many of them broken and jagged on the chamfered edges causing even more damage. Not just to runflats but to all tyres. Though, of course the wider and lower profile the tyre, the more damage is likely to occur. Everyone urgently needs to inspect the inner (hidden) shoulders of their tyres. Instead of straddling it’s better to risk spring damage by driving one side over, one side on the flat. There is some news on runflats. I've just been experiencing Bridgestone's third generation runflats, all 245/40 R18s. By allowing 'softer' sidewalls and new polymer, ply and cooling technology to allow the tyres to 'run flat' they have finally managed to achieve the ride quality of a conventional tyre, thus overcoming the principal customer objection. The new runflats can also run without air for up to around 80kms and usually remain repairable, overcoming another objection.