Today while cruising on the motorway in the RR TD6 sat at 70 mph, I attempted to accelerate past a vehicle the RR refused to pull and all I got was juddering and no increase in speed, it felt like a plug was off but as its a diesel thats not possible, would anyone know what it could be! I have no warning lights on dash and it seems to be running fine at town speeds.

Sounds like fuel starvation. When was fuel filter last changed? I wonder if the pump pressure is good. Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI

Thanks for that,,,,yeh I was thinking fuel starvation but I'm no mechanic, it was serviced 6k ago by LR,,I will get that swapped first tomorrow

I would then start using a redex type diesel fuel additive for the next few fill ups and use shell or bp fuel, not supermarket stuff, just incase some injectors are a bit dirty. It does not harm to do that a few times a year. Previously..
Vogue SE TD6
Defender 90 2.4
Defender 110 TD5
Vogue 3.5 EFI

Low pressure fuel pump is a usual suspect . . . .

 Where do you go after one of these . . . ?

Thanks for your help guys much appreciated, I think I will replace the fuel pump as well while Im at it

I don't know if it applies to the TD6 but on my old 300 TDi another thing to check would be de-lamination or splits in the intake pipe from the turbo, leading to a whistling sound when the turbo cuts in (if it's split) and a lack of power. 

Been there, done that! I had difficulty getting the gearbox to kickdown on hard acceleration too which is another fuel pump symptom. Suggest you get the garage to test the fuel pump pressure.

Update... My indie put my RR on the diagnostics and it threw up the following three faults; Boost control valve, EGR valve, and Delivery fuel pressure, so I have had a new fuel filter fitted today as we already had it so put it on. The fuel pump I intended to put on didn't arrive so as my indie had some time he removed cleaned and refitted the EGR valve, you would not believe the sh@te in the valve. It would seem that the EGR has definately been part of the problem as apart from a barely noticeable judder and the revs bouncing very slightly, now after a good cleaning it seems to have all but nearly cured the problem, and now doesn't blow out black smoke when pressing on. I'm hoping the slight judder etc is down to the filter and it clears it self and settles down, though that's probably wishful thinking!



.

An EGR Blanking Kit would help a lot.
It just removes the EGR from the system and saves chucking hot exhaust gases into your nice cool air that the intercooler has created for you.  

Well the new fuel filter and EGR being cleaned didn't cure the lack of power problem on the TD6, it progressively got worse. I have had a new external fuel pump fitted two days ago, took 15 minutes to fit, which has rectified the issue and its running better than ever. Something I didn't expect on a motor with 60k miles, though in reality a cheap fix.

Many thanks to all who posted.

It is not only the miles but also the age that could have an effect. From what I read on this forum, those pumps don't have a very good life expectancy. Glad that you are up and running again !!! MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!