Sci fi book, man buys a beat up spaceship and intervenes in a civil war on a planet and eventually becomes a space cop

Question

UK paperback, possibly early eighties.

This man goes to the used spaceship dealership. The salesman shows him many types but his eyes are continually drawn to a beat up old heap in the corner which he eventually buys.

He takes it for a familiarisation cruise and finds a lot of strange tech hidden under the floors and behind wall panels, it soon becomes apparent it's highly advanced and also has a near AI computer that can do camouflage.

He then has adventures on different planets but I only remember one…
This world is having (I think) a civil war and he decides to intervene to save life. Initially he sets up a plan to approach this world as a galactic warlord and give them a common enemy.

The planet's defence see a small spaceship and a (projected) battle cruiser approaching. He shows up on their screens in fancy uniform giving out orders. He snarls out “Master-at-Arms!” and a grizzled veteran with a sardonic smile appears on the screen with a crisp “Yes Sir?” and he gives some order about demonstrating firepower, all in full view of the planet leaders.

At this point alarm bells are ringing in the protagonists mind, the faked soldier seemed a bit too realistic!

I don't recall how he then solved this war but later he's out in space and he chats to the computer with his suspicions. Then a big reveal and a real battle cruiser uncloaked beside his spaceship and the same Master-at-Arms tells all.

They need people of a particular mindset to be secret Galactic Police, the junk spaceship is designed to appeal only to the people with such a mind, therefore he is now a super cop and commands this precinct.

Update: The answer was 'Interstellar Patrol' (2003) by Christopher Anvil and I've checked it as correct, however that book is a fix-up containing the much earlier story 'The King's Legions' (1967) which was actually the original story I was trying to recall

Answer 1

Interstellar Patrol (2003) by Christopher Anvil.

The starship crew was stuck on a planet where the well-meaning schemes of social engineers had created a nightmare of battling gangs. So they pretended to be the Royal Legions from a distant star kingdom pursuing an all-powerful villain hiding on the planet. Then the real Royal flagship showed up.

There's a sequel - The Federation of Humanity

Vaughan Roberts and his two companions had been trapped on a crime-ridden, chaotic planet until they bamboozled the population with a gigantic hoax-which brought them to the attention of the Interstellar Patrol, who were looking for a few good con men, capable of ingenious improvisation and adept at playing dirty tricks on the bad guys. The new recruits acquited themselves admirably, so they naturally were given more tough nuts to crack, including:· Flummoxing an alien empire which has taken a number of human prisoners as reconnaisance for an invasion. This has a personal aspect, since the prisoners are from the planet which Roberts tricked into reforming. . . .· Stopping a plan by not-so-good Samaritans who are pretending to cure a planetary plague-which they introduced to the planet-with a "miracle" drug which creates an addiction to the same drug, which the schemers will be glad to continue supplying for ever-increasing sums . . .· Not only rescuing some Patrol personnel taken hostage by fanatics who plan to execute them one at a time until their leader is released, but convincing other fanatics throughout the galaxy that the consequences of threatening anyone in the Patrol are too terrible even to think about. . . .· Making sure that the rightful heir to a planet's throne escapes from captivity and overthrows the usurper. This time there's a complication: Roberts may be falling for the ruler's beautiful sister. . . . And much more. . .