“The English Catalogue of Books” says that this book was first Published in January 1940 (possibly because the year was known but not the exact month)

The British Library copy is dated as being received on 11th June 1940 - 254 pages

The Bodleian Library copy is dated as being received on 28th November 1940 - 254 pages

Due to wartime paper shortages, it was not uncommon for the publication of books to be delayed

The true first edition has blue boards with the title in yellow on the spine and the John Hamilton “sun dial” logo at the base of the spine – see photographs of the book towards the bottom of the page


Original first edition dust wrapper showing the price of 7/6.  The identical dust wrapper appears on all subsequent reprints.  You can only tell a first edition by looking at the boards of the book.


The French version of the book “C’est X Qui Frappe!” translates as “It’s X who knocks!”


Republished in paperback by Norman Wright in 2003 - 188 pages


This excellent, fast moving and exciting adventure begins with Nigel Deane, known as "Gunga", summoning his brother Guy, to discuss the death of their older brother Peter. Pete was a journalist and Gunga is convinced he has been murdered because of a letter that Pete sent to Gunga the night of his death. Pete was investigating a mysterious gang, who identify each other by a 1904 Victorian Penny and whose members are only known by numbers. Pete was killed in a car crash at a place called Blandford. Gunga and Guy resolve to kill everyone involved in Pete's death and bring this criminal organisation down, come what may. Being service men they both have guns and the ability to kill in cold blood. It is clear from Pete's letter that the only person who knew of his destination on the night of his death was his editor, Brimfield. Gunga and Guy go to Brimfield's home address, show a 1904 Victorian Penny, and bluff about the death of Peter Deane. Brimfield ('Number 23') reveals his involvement and they shoot him dead. Gunga is able to use a private line to ring 'Number 17' in the gang and tell him what they have done. He calls himself 'The Unknown Quantity'. Paperwork from Brimfield's desk leads our two heroes to a seed shop that supplies cocaine to its customers. Gunga suspects that Inspector Drysdale of Scotland Yard is a member of the gang and he writes to him about the drug dealing seed shop giving the address of the Cottage the brothers are staying at. Gunga suspects that if Drysdale is bent there will be an attempt on their lives. Sure enough a bogus policeman calls ('Number 119') and has to be shot. His body is dumped outside Inspector Drysdale's home address. After stealing some post from the seed shop, a lead takes our heroes to see a Lola Darling in a private nursing home. Lola tells Gunga and Guy about her diary before she is murdered by 'Number 17', an Archdeacon Brindon. Our heroes tell him who they are and shoot him dead. Unfortunately, a photograph of a local cricket match captures both them and their car and the police are on to them. Inspector Drysdale pays our heroes a visit at their new base and an enigmatic conversation ensues. Shortly after an attempt is made to blow the new base up. Gunga and Guy search for Lola's diary. Logic and luck help them find it at the flat of the now deceased 'Number 119' but Drysdale gets to the diary first. In the flat they find a newspaper with an account of their brother's death at Blandford and of another mysterious death in the same area that day, the son of Sir Roland Alister-Bowes, killed in a shooting accident. Gunga knew the victim from the army and using that pretext goes to call on Sir Roland and his daughter Ann. On the way, a following car gets a hand grenade from Gunga. When they meet Sir Roland, they take him into their confidence and he does likewise. Lord Glenbold, the proprietor of the Daily Echo, Peter Deane's paper, is blackmailing Sir Roland. Lord Glenbold is staying with Prince Rubenoff who happens to live on the neighbouring estate. The main suspect for the murder of Sir Roland's son is Prince Rubenoff's gamekeeper, a man called Tredwell. Gunga and Guy pay him a visit, pretending to be gang members by showing the 1904 Victorian Penny. They learn that Lord Glenbold is 'Number 3' and they pretend that they have been sent by 'Number 1' to order Tredwell to kill 'Number 3', which he duly does. They then leave Tredwell to be arrested and face the hangman. Getting into the residence of Prince Rubenoff, the mysterious and masked 'Number 1' arrives for a conference. Inspector Drysdale also arrives. The house is then secured by electronically closing shutters. Here Gunga and Guy set to work avenging the death of their brother but there are still some surprises and twists before the day's work is done.


The Unknown Quantity

Subtitle - none

Publication Details - originally published by John Hamilton




Original first edition book held by the Bodleian Library in Oxford.  This was stamped as received on 28th November 1940.  There are numerous reprints of this book, but I believe that the genuine first edition is this one,

with the John Hamilton sundial logo at the base of the spine and the title and author’s name all in yellow.  There appear to be numerous reprints of the book but none of them have the John Hamilton sundial logo on them.


Above is the first edition from my own collection.


 Above is the most common reprint


Above is a selection of different reprints for THE UNKNOWN QUANTITY, they appear to be quite numerous!


2003 Reprint published by Norman Wright.  Artist Andrew Skilleter was asked to repaint the original jacket.