Defender TD5 Help needed!

My Landy, wich I love in many ways, is giving me some grief nowadays.

Basically, my situation is this :

Hard to start, one can hear the feederpump (?) Situated in the tank when turning the key. It migth take a go or 3 to get it running, but then it would run for as long as needed.

Untill today !

It stopped 3 times on a 2 hour trip, all times it came back to life after 5-10 minuttes of trying to start it, smoking about 2,5 cigarettes and using 4-9 norwegian cursewords. No logical explanation.

Is there anyone who migth have any idea of what can be wrong?

I have a theory based on the fact that I have been noticing the tank-pump beeing there for the last 3-4 weeks. I havent heard anything from it before, and have been driving it as my daily driver for the last year (20 000) kms.

The car is a 2006 with the TD5 motor.

Thanks go out to anyone who migth have a theory as to what I can try to do.

Best regards
There is one theory I have gotten from one of my colleagues - Vacuum in the fuel system. Basically, the tank air-vent not working properly, and that then causes the fuelpump in the tank to malfunction.

What does the people of the forum of a theory like this?
As a quick way to check if your fuel tank breather is blocked, drive it and when it cuts out next remove the fuel cap. A little hiss is sometimes common as air pressure balances but a large 'whoosh' noise implies it's the breather.

Are you getting any engine management lights on the dash when it cuts out?

A noisy fuel pump implies it's on it's way out but they usually go quiet when they fail.