Absolutely normal for heavier wheeled helicopters to taxi to a suitable area for departure. Not at all sure about the assertion that it was 500 yards, but there would be a few reasons for any S61/Sea King (or similar) to do so.
Downwash of two Sea Kings lifting would be substantial, and disrupting to the VIP escorts on the ground.
Departure on a clear area (runway) allowing a safe rejected takeoff.
Line up for a departure into wind, vs a restricted choice should a departure in the area of the startup and loading.
Michael Gee, FWIW the wheels are not 'delicate'! Not at all sure what you mean about the intake guards, they are the normal FOD shields that have been around for some 45-50 years.