David Lang was relaxing in the remote Himalaya mountain village of Jakar when a villager told him his home town - and probably his house - was under water.

The amateur botanist was taking a break in eastern Bhutan after an exhausting trek through dense mountain forest searching for rare flowers.

All around lay the lush green hills of the Tista Valley and above, the skies were hot and blue.

Lewes seemed a million miles away.

But the mood was broken when a curious local approached, asked him where he came from and said: "Oh, my god! Your town is under water!"

It turned out the isolated village, which in many other respects has remained medieval, had a solar-powered computer and was hooked up to the internet.

Fortunately David's house in Barcombe was relatively unscathed by the torrential rain which fell in the south of England in November 2000.

And, after a brief visit home, the 68-year-old was back on his travels into the thick of the beautiful Himalaya region in pursuit of Yaks, Buddhist temples and rare flowers.

David has made four treks through the mountainous northern parts of Sikkim, an Indian state of snow-covered peaks and flower-filled meadows, and written about his exploits in a new book.

Travels In The Cloud Kingdom: Sikkim Himalaya is a sort of botanical travelogue and has much to amuse any readers unable to tell a Dendrobium densiflorum from a Cupressus himalcaica.

Sikkim has been the centre of a protracted dispute with China which refuses to recognise the legitimacy of India's 22nd state.

Consequently, travelling through the country is not easy and requires a great deal of patience, form-filling and diplomacy.

On one occasion, David fell under house arrest in the northern part of Sikkim while he had a bad case of dysentery.

"I was having a terrible time and kept having to dash behind a rock on the mountain side with a soldier standing guard with a Kalashnikov, loaded and ready to fire.

"One alarming noise and all hell could have broken loose. The military over there is very cautious of outsiders."

Elsewhere in the book, small influences of Western culture surface when local herdsman gather to celebrate a Buddhist festival to bless their yaks.

The lama sat behind a small wooden table between two cymbals and a drum, which he struck at regular intervals.

In front of him, a large tin bath was filled with offerings to Buddha which included money, cheese and, from somewhere, packets of Cornish wafer biscuits.

Mr Lang, who worked as a vet for 37 years in Lewes, has now dedicated his life to amateur botany and written five previous books on the subject.

He first became interested in the Himalayas as a child when he used to listen to his father reading aloud from books written by the great botanical explorers.

"In my mind's eye I could see the high mountains, the valleys carpeted with primulas and gentians and, above all, the yaks," he says.

"There was something about yaks that appealed to a small child and I longed one day to see them."

And then a school master helped to develop his interest.

"I went to school in Tonbridge and had an excellent teacher who was really into botany."

For years, post-war travel restrictions and family circumstances prevented Mr Lang from fulfilling his dream to explore the Himalayas until 1983, when he made a trek to Kashmir with the legendary botanist Oleg Polunin.

Travels In The Cloud Kingdom: Sikkim Himalaya, is published by Pomegranate Press, priced £29.95.