In Biggles Follows On, Biggles and Ginger were aided in their escape from Prague by an British intelligence agent by the name of Smith. Described as a mild-looking little man of late middle-age with steel-rimmed glasses "balanced on the end of his nose", Smith also has a deformity, one shoulder being higher than the other. This, he explained to Biggles, was the result of a spine injury after falling from a horse while hunting, an accident which destroyed his dreams of serving his country in the Army. But the deformity made his persona, that of an impoverished and pathetic looking Czech tailor, all the more credible.

Travelling to Prague to seek a cure, Smith picked up the local language and customs. He decided to stay on even though the treatment failed. He was subsequently recruited and served with British intelligence during the Second World War. After the war, he was preparing to return to England when Czechoslovakia came under Russian domination and he was asked to stay on. In the time of Biggles Follows On, Smith managed a safe house and listening post in Prague under the persona of a tailor by the name of Johann Smasrik. Located in the old quarter of Prague, the address had been given to Biggles and Ginger before their departure from London for use in emergencies.

Although it would appear he had never been trained as a professional agent, Smith was nevertheless a meticulous planner. When Biggles and Ginger arrived at the safe house, Smith had them installed in the attic, which had a prepared escape route through the skylight and over the roofs of neighbouring houses onto the street. He had installed an emergency buzzer to warn the occupants of the attic of trouble. He had a radio (but not at the shop) and a hiding place for Biggles' and Gingers' bags.

Biggles and Ginger were not the first people Smith had to arrange extraction for. Smith knew of a suitable field 12 miles away, on the outskirts of Prague which he thought was suitable for a landing, and he was able to send a message to Algy to come and pick Biggles and Ginger up. He also arranged a farm cart to convey Biggles and Ginger to the field at the right time.

Smith's thoroughness and stolid nature earned the respect of Ginger and Biggles. Ginger commented that Smith must have nerves of steel to stand the strain of his post. While their own work had moments of high tension and danger, there were, nevertheless, breaks in between. Smith, by contrast, had to bear his burden without respite.

Smith's planning saved the day when Erich von Stalhein did indeed raid the tailor shop. Forewarned by the buzzer, Biggles and Ginger were able to escape through the skylight and eventually make it into the farm cart heading for the landing field where they were picked up by Algy and Bertie. Smith was, as planned, left to talk his way out with von Stalhein. He obviously succeeded for, at the end of the book, the reader is told that Smith escaped from Prague and returned to England where he wanted to meet for a meal with Biggles and his friends. From the ending of the book, the reader is almost led to expect that he would meet Smith again in a later story. Unfortunately he never appears again, which is a pity, for that would also have been quite a story.