In the hot weather, tiny thunderbugs or ‘thrips’ managed to get into the LCD panel somehow.
We stayed up high for a couple of miles, a hatch of thunderbugs coated a gate post, a train hooted and rattled and we descended a sunken wooded track to the Newbridge Crossing.
However, if you see a black cloud of thunder bugs or flying ants around, zip up the tent door quickly.
On a straight stretch into Darlington, the heat haze wobbling the view, there were millions - even billions - of thunderbugs.
Use Sellotape around the glass to (a) keep out dust and dirt and (b) keep out thunderbugs.