Many entries to this diary are rather local to my localities, Hertfordshire and London in particular. It's best to speak of what you know. For example Gilbert White's much loved and pioneering book 'The Natural History and Antiquities of Selborne' concerned his own parish.

 Anyway I took a stroll from my home town of Hitchin and noticed the River Hiz was as full and fast flowing as I can recall it. I walked out to the source of the Hiz not far from the village of Charlton.

 The spot where it rises is generally no more than a damp dell. Usually the river begins as a shallow stream flowing from a farm pond about a hundred yards from here. Indeed the pond itself is often just a muddy sump. Lately however a headwater has formed, testament to the wet winter we have had.

 I didn't have a very close view from the road so I circled round to the other side via a footpath behind the aptly named Wellhead Farm. Along these low hills the Chilterns escarpment slopes down to the flatness of East Anglia.

 Water seeps through the chalk bedrock at this spot. Clear spring water, not runoff.

 I could see ripples on the surface where the river rises.

 Over the course of a mile or so the Hiz becomes a fully fledged meander through fields and several wet woodlands with marshy margins. Then it is channelled where it passes through Hitchin. One of the defining characteristics of the town is that a river runs through it. From the late nineteenth century the introduction of a railway line became more significant and latterly several major roads and a nearby motorway.

 But the Hiz is still a feature feeding as it does into the River Ivel about ten miles away and ultimately into the River Great Ouse towards the Wash and the North Sea. Notably, the Hiz is a chalk stream. There are said to be 210 chalk streams globally, 160 of them are in England and a good many of those are in the 'Southern England Chalk Formation'.

 No doubt there is something to be said for the Nile, the Yangtze and the Mississippi but they are not chalk streams. So I consider my journey to the source of the Hiz to be a successful expedition.