Bruce in Bangkok wrote:

There is a book about that same thing only it was diamonds Smuggled
out of Britain to evade currency restrictions and smuggled back inside
an engine from a lethal wreck near Tahiti.
Trustee From the Toolroom by Nevil Shute is what I sort of remember,
so i checked, Suspicion confirmed.

Casady

Lord, I remember reading that book years ago. As I had been a
machinist early in my career I thought it was a really good read.
Funny though I remember that the guy had a machine shop in his house
but not the diamonds.

Same here Bruce, read it more than 30 years ago when I was a teen.
Didn't remember the plot, but remembered the machinist aspect, envied it
in fact. Now I have a machine shop fifty feet from my front door,
better than having it in the basement,, at least in the opinion of "She
who must be obeyed"

I really liked Shute, until I learned more about the man himself and I
was left with rather bitter taste in my mouth.

Cheers
Martin