Those using a standard socket to loosen the top cap on the fork, be cautious! The flats on the top cap are not very big at all, whereas the inside chamfer on the socket is quite large. That chamfer is to clear the radius on steel bolts. What you have left for engagement is really small and the top cap is soft aluminium! The last thing you want to do is to rpounjd off the top cap!
Take great care, press down on the socket to ensure max engagement. But best of all, grind the socket flat and remove the internal chamfer. I borrowed a mate's hand-held grinder and I thought it would take ages. It took less than a minute and I was being really careful. It took longer to rub the socket across a honing stone to smooth out the grinding marks.