What is wrong with Peugeot 306 1.9D N Reg and how to fix it?

I have a Peugeot 306 Diesel1.9D N Reg. I was driving on the motorway and as I overtook another vehicle - I noticed that the engine has lost power - like it was firing on 2 or 3 cylinders and I was about 15 miles from home - I decided to press on.

The car downhill could barely reach 60mph and could see some smoke at the back as well as the rear screen.

I managed to get home with difficulty as at every intersection the engine was on the point of stalling and had to accelerate the engine to keep it going.
On opening the bonnet the engine was covered in diesel fuel. I have tried to start the engine but it refuses to fire.

There is no visible sign of a broken fuel line.

What is the problem with car and could I have caused damage by driving on.