Conkers ARE getting smaller
Since my tweet ‘Is it just me or are conkers getting smaller?’ I’ve made an important discovery which solves the mystery. The conker tree outside my house was badly affected by the conker moth caterpillar earlier in the summer. 
Earlier today I discovered a conker tree that was hardly affected at all, whose leaves retain their vigour.
The piddly one on the right is from the infested tree, the definite keeper on the left is from the healthier tree. So it's not just me - conkers ARE getting smaller.
Fig1 clearly shows the damage made by the tiny worms eating up the leaf.
Fig2 shows a conker from each of the trees.
The piddly one on the right is from the infested tree, the definite keeper on the left is from the healthier tree. So it's not just me - conkers ARE getting smaller.
Case closed!