Answer: From Heathrow to Cardiff, the closest airport, the flight distance is 125 miles. Then you have to travel from Cardiff to Dartmoor by car. The driving distance from London to Exeter, the closest town to the park, is 198 miles.
Who the hell would fly that distance, and anyway, the nearest airport would be Exeter airport. There are actually many towns inside dartmoor.
Answer: go onto google maps and enter in your specific info - like your postcode and the postcode to which you are going and then it will tell you the routes you need to take and the time it will take you to get there.