Power loss when warm but no warning lights and diagnostics clear

HI, I have a 2014 SD4 Freelander 2 auto with 66,000 miles and excellent service history. It has been running well and nothing has changed until recently, when warmed up it gradually looses power. No warning lights, noise or smoke. Local garage has done a diagnostic and nothing came up. Anyone had a similar problem and fixed it?? What is it likely to be??

Fuel filter is the likely cause, I've seen this issue several times.
There's a thermostatic valve in the filter, which is designed to recirculate returned fuel to the injectors when the fuel is below 20°C. However when the fuel get above this temperature the thermostatic valve is supposed to allow 95% of the returned to pass to the tank, so 95% of the fuel the engine uses is cooler fuel from the tank. However when the thermostatic valve fails or isn't correctly calibrated (some aftermarket filters are like this), then the fuel temperature exceeds a level that the ECM is happy about, so it reduces the engine power output to prevent damage to the pump and injectors.
I'd check the filter is an OE filter firstly (the OE filter has Purflux on the top), and replaced it to eliminate it as the issue.

Thanks Ill try that first and let you know if it resolves it.
After £500 and two garages having a go at finding and fixing this issue I booked a full service hoping that it would eliminate a potential fuel filter issue at least. It turned out that a noise developed a day before the service that sounded like high pressure air when the engine was put under load. That was the Turbo boost pipe leaking. Now the service has been completed and the Turbo boost pipe replaced the car is back to its best.
I hope this helps others with a similar problem.