MY ASSISTANT had provided me with a cardboard isosceles triangle. I was assured that this would enable me to estimate the height of any object.

In Scotland, on the road from Perth to Braemar, I crossed the river Isla and came to an immense hedge along the roadside. The Meikleour Beech Hedge stretches for 580 yards along the eastern boundary of Meikleour House. It was planted in 1746, and is now more than 100ft high. It is still clipped regularly.

I parked my bike against it and checked my assistant's instructions: 'Walk away from object until you can see the top at 45 degrees (using the cardboard triangle)'. This entailed walking backwards across a ploughed field.

After several attempts I estimated the height of the hedge as 107ft. Then I took a walk along the inside. It comprises about 450 huge beech trees, some with double and treble trunks. Among the foliage was a partly hidden notice. Erected when the hedge was only 85ft high, this told of 'trees being seriously damaged by persons climbing them, breaking off branches and carving names in the bark'. The notice had almost rusted away. The trees pressed upward.

The Meikleour Beech Hedge is at Ordnance Survey grid reference 161385.

(Photograph omitted)