I learnt many years ago and two punctures on a ride and the cause can't be found-and the tyre comes off. Many of the "Blackthorns" we have over here will break off very short in the tyre but gradually get pushed through the rubber. It punctures the tube but hand round the tube and nothing found as on deflation- it disappears back into the tyre. Tyre off- turn it inside out and you will find it- And the other 6 that are also there.
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How long was I in the army? Five foot seven.
Spike Milligan