Griswallt ap Llechitwyt is the psuedonym of artist/author David Bellamy
Old Grissie, as he is affectionately known, is a well-known authority on the Llandoddies, the legendary water-folk of Llandrindod Wells in the heart of Mid-Wales, and he has many tales to tell of their exploits. Terror of the Trolls is is the second book in the series, following The Grog Invasion, which has attracted fans from Newbridge to New Zealand.

He dislikes large crowds and his few visits to Llandod certainly tend to introduce a chaotic flavour: he has been known to empty a café rather quickly when he calls in for lunch. Whether it is the bag of smelly rabbits he carries around, his long staff, or his wild appearance that compels people to seek the opposite side of the street when he is in town, is a moot point.

Happily, much of his work in rendering the illustrations of the Llandoddies is done at night when most folks are tucked up in bed. Lurking quietly in the undergrowth, he is content to suffer all manner of deprivations in order to capture a likeness of his little friends, and observe their antics. How he managed to obtain the underground images, is, however, a complete mystery, but then, Old Grissie is a mystery to most folk.