When I got back to UK, I found that this behaviour had been reported by The Lizard Lab at Macquarie University in Australia, again with some footage of this lizard at Angkor Wat.
They speculated that this behaviour may be to draw the attention of predators to the expendable tail as in other lizards with conspicuous tails. Well, maybe? Could it be display or even to attract insects as a lure?
I am afraid that I disgraced myself at Angkor Thom by not recognising the site of a film scene from Tomb Raider nor, indeed, knowing that such a film had ever been made. When Angelina Jolie was mentioned, I am afraid I only vaguely recalled that she was an actress, and could never recall having seen her. In defence, I did point out that former directors of Scottish research institutes were no stranger to video games. Indeed, the late Sir Kenneth Blaxter phoned me in great excitement one day to say that he had finished his masterpiece (written in BASIC, I think) Fragmentation Bombing of ARC Headquarters. For those not born then, the Agricultural Research Council was the forerunner of the present BBSRC; its headquarters were in Great Portland Street, London before they were removed to the outer darkness of deepest Swindon.