Festival season is well and truly upon us, and it's also turned into the summer of the heatwave. If you haven't got a tent sorted yet, or if you were planning on digging out that old, slightly musty bag of fabric that's been festering in your loft, might I suggest that now is a good time to invest in a blackout tent? Over the years, I've camped in all kinds of conditions and in all kinds of tents — both for fun and in a previous role as an Outdo…