Heston Blumenthal's Perfect Burger

Yay, it's finally BBQ season... It may look like I only cook chocolate delice and frangipane tarts, but hey, my kids like a burger as much as the next person.  Of course that wouldn't be a generic supermarket burger, and so finally the opportunity to try Heston's perfect burger recipe.  I'd seen this recipe on his How to Cook Like Heston show, but we didn't fire our BBQ at all last year, and so the itch grew and grew.