I'm not 100% sure if and whether or not Land Rover fitted free wheeling hubs as standard at all (don't they have to be added as an aftermarket product?) but it could well be that your right side free wheel mechanism isn't quite as free as your left hand side, hence the drifting to one side. It's only a theory, but it's all I can think of! The only way to tell is to jack the front end up, one wheel at a time or both together, doesn't matter, but make sure that the car is in gear with the hand brake on. Spin each wheel, if it spins and continues to spin, you have free wheeling hubs. If it spins so far and then stops / bounces back, they aren't free wheeling. If they are free-wheeling, obviously then you can try and identify and differences between them and the time that it takes for them to slow from free wheeling to a stop. If there's a dramatic or noticeable difference ie. one side spins and takes ages to slow, where as the other one slows quickly, there's your problem!
Oh, another theory is that you turn the wheel very slightly without realising!