birch

He says children were disciplined with birch sticks, which "was meant to be a loving form of correction".

He says a study by the University of Worcester showed oak and grass pollen seasons are starting earlier and birch pollen is becoming more severe.

For years, it was easy to forget that we used to be a woodland nation: around 6,000 years ago untouched swathes of oak, hazel, birch and pine blanketed an estimated 75% of the UK.

This year the warm weather in the UK, plus last year's too, means conditions have been ideal for birch tree pollen - a major hay fever trigger.

For instance, research by the University of Worcester found that the birch tree pollen season is getting more severe, while that from grass continues to fluctuate around the long-term average.