7.2/101 Votes Alchetron
Cover artist Gavin Rowe
Publication date 1980
Genre Science Fiction
Country United Kingdom
Originally published 1980
Page count 224
Publisher Walker Books
The Horn of Mortal Danger is a 1980 novel by British musician Lawrence Leonard. It relates the adventures of a brother and sister as they discover a secret civilisation buried beneath the streets of London. It is a 'classical' children's fantasy.
Simon ("Widgie") and Jen Widgeon are innocently exploring the abandoned Highgate rail tunnel near their home when they discover a hidden gateway halfway along it. Through this they find their way to a little old-fashioned railway station.
At first the tunnels seem deserted. However, as Jen wanders down the tunnel to explore, the Railwaymen emerge and capture Widgie. Jen, in her turn, discovers an underground canal, complete with a little steamboat, which the railway crosses by means of a retractable bridge. Men emerge from the boat and take her captive.
It quickly becomes apparent that Widgie and Jen have become caught up in an entire underground civilisation, the North London System, kept secret for centuries from the world above. Two civilisations, in fact, seemingly perpetually at war. The siblings' arrival is the catalyst for a climactic battle between the Railwaymen and the Canallers.
Widgie manages to escape and rescues Jen, and the realisation of the threat they pose should they escape aboveground and expose the System forces the Railwaymen and the Canallers to set aside their differences for the time being, to collaborate in an effort to recapture them. In the course of the battle giant rats, kept imprisoned in a blocked-up tunnel, are released and proceed to spread through the whole system. As Widgie and Jen escape into the Post Office Railway, it appears that the entire civilisation is on the verge of disintegration under the assault from the rats.
It is worth noting that, seemingly in imitation of The Lord of the Rings (1937 and 1949), Leonard includes appendices relating the aftermath of the story underground, in which the Railwaymen and Canal Folk discuss the joint threats of the children and the rats, and giving a short history of the North London System (and suggesting that similar societies exist beneath many major cities, at least in England). It also includes two short "Interludes", set aboveground, concerning the search for the missing children.