Tate Modern's triumphant opening this week is a vindication of all the money, delay and heartache involved in the project - a magnificent achievement which will be a permanent tribute to the skills of Nick Serota and his team. OK, the original construction budget was £40 million, but who's arguing? One visitor to the new gallery, Alan Stapleton, was site engineer for the original Gilbert Scott power station project. He told Radio 4's 'Front Row' programme how proud he was to see the building he helped create transformed for a use which will guarantee its life for as long as anyone can imagine. He tells Astragal that when work started in the late 1940s, the local street was cobbled, having been laid a century earlier by prisoners from the nearby Clink prison; that a local lively lad used to shoot pigeons and sell them to West End restaurants where they ended up in game pie; and that there was still an extant bear pit in the area. The new building will be a bear pit of a different sort . . .