Claiming back losses from car mis-sold with higher mileage than on the clock

[Guest]

I purchased a vehicle with 28,000 or so miles on the clock, had it 2.5 years, and decided to trade it in. Have come to get a trade in price and the National Mileage Register has a mileage discrepancy of around 40,000 more than the actual clocked amount. When I bought the car it had just had it's first MOT by the dealership, recorded at 28,000 miles. The NMR has a recorded mileage of over 68,000 miles before the first MOT. After learning this I was obviously out of pocket, so handed the car back to the finance company, so I have no more connection to the vehicle. However I am concerned that the dealership, when performing their checks, didn't spot this, or if they did, they concealed it from me, essentially selling a vehicle to me worth approximately £3K more than it was actually worth.
Am I able to go back to them now after the event? If so, how do I approach this?

[des8]

Did you query this with NMR?
A quick Google indicates that they are prone to error as they rely on dealers imputing correct figures etc.
Easy to see dealer making the error.

When you purchased the car, did you not examine the service record?
That would have flagged up questions if 68,000 miles had been wound back to 28,000

And if you try court how do you prove NMR are correct... they are unlikely to attend as a witness on your behalf?