I don't want to intrude, but the fastest revving diesel I've heard of is the Renault DOHC Diesel at 6.500 rpm. There were rumours about the Audi R10 engine achieving 8.000 rpm, but it works in the 3.000 to 5.000 rpm range.
Diesel engines have more torque because they weigh more and the piston undergoes faster acceleration, Andy. You don't need such high revs: the idea of Rudolf Diesel was that an engine with higher compression would be more efficient. You pack more air into the combustion chamber, you use a fuel with higher energy content, so you get much better torque.
The R10 is an example: even when made of light materials and including a design with clever cross-struts (or whatever is the english name: struts are reinforcements you put in the crankcase and block to withstand the extra-force of Diesel power stroke),
the weight per piston of the Diesel engine of this Audi was the same as the one of a gasoline powered one. So, in the end, after much effort, Audi engineers arrived to a design similar to the gasoline one they had before, altough "top-heavy".
Audi TDI engine: some day this will be an example of how we tried to squeeze every drop of oil in the first decades of XXIth century. It's a magnificent engine and include the turbochargers Andy wants to see
That is quite an achievement in an endurance race because a Diesel engine is more "stable" than a gasoline powered one: you pay your price in designing for high stresses, but the engine you get works at a slower pace.
Actually, you pack so much "punch" in every power stroke that you can allow yourself to run it very slowly, thus the wearing is smaller. Think that Diesel engines put 3 times more air into the chamber than Otto engines (1:24 compression ratio, tops for a Diesel, vs 1:8 compression ratio, lower end of gasoline powered ones).
The real good thing about Diesel engines is that they are the most efficient design of any internal or external combustion engine. You compress only air, and by compressing it you make air so hot that almost all the fuel you inject burns. So, a diesel engine is a lean engine, which means it uses less fuel. The theoretical top thermal efficiency of a diesel is a whooping 75%.
On the other hand, an Otto engine is limited by the atmospheric pressure: how much air can you get into the engine? It depends on its suction ability, if you get my drift, as the cool equations show.
The equation for thermal efficiency of an Otto engine. It depends on the adiabatic constant of air and the compression ratio
So, as you can (almost) see in the equation, the larger the compression, the larger the efficiency, isn't it? So, you want as much compression as possible.
The problem all Otto, gasoline powered, engines have is the problem of detonation. If you compress the mixture of gasoline and air too much, it detonates, instead of burning. That is, the explosion moves faster than sound. That shakes the engine and the loads damage it.
If you use regular gas instead of extra, and if you live in a city by the sea (high pressure) and if you don't have a modern car that checks the mixture, you hear a rattling noise from the engine when you accelerate: that's the gas
detonating inside the cylinders; same thing happens if the spark timing is wrong.
A bullet moving faster than sound shows clearly (at least to me! 
) the difference between detonation, explosion and deflagration: the bubble is the border of the explosion (at the speed of sound). The bullet is at the tip of the cone, to the left, moving faster than sound, the surface of the cone marks the border of the detonation wave. You can see the deflagration cloud, with a "square" shape inside the bubble (made of gases burning in a frontwave). A Diesel engine deflagrates by design
A Diesel engine works in a different way: you inject only air and compress it a lot, thus packing a lot of oxygen into the combustion chamber. Then you allow it to deflagrate in a slow manner. No explosions, no detonations: you're limited by the strength of materials.
The problem is the narrow power band Diesels can work at. Why?
Under heavy loads the bearings doesn't last if you make the engine turn fast. The life of a bearing depend exponentially on the rpms it withstands and the load it has. Diesel imposes heavy loads on moving parts. For example, I can attest that a big block 502 engine can run all your life at 2,800 rpm, but run it at 3,800 rpm and you can kiss it goodbye in 500 hours. So, you need a really good gearbox, because the engine doesn't rev up too much.
I think that any engine has virtues and deffects, like relatives and girlfriends (you love them anyway). If you use a Diesel engine you are putting up with different problems than the ones of your adversaries, so research is squarely on your shoulders. I think that for Diesels to be used in Formula One, you need a political statement of one of the teams, like Volkswagen and Audi did in other series. In simple english, it means you need a wad of cash.
I will be very disappointed if, after such long explanation, Andy cannot say with confidence that diesel engines have a
higher compression ratio. Right, Andy?
