It was an extraordinary moment, captured on camera a few weeks back. Clearly nervous in the presence of bigwigs including Mayor Bloomberg and Governor Pataki, stammering slightly, Calatrava forsook the language of words and reached instead for the architect's comfort-blanket: the big felt-tip pen. Quickly, with a few deft movements, Calatrava produced Picasso-like sketches explaining his concept. A bird, being released into the air by a child. It sounds almost mawkishly sentimental. But this germ of an idea has generated one of the great railway station designs.

Standing by at the presentation was Libeskind, applauding wildly, that now-familiar huge grin on his face. He, more than most, appreciates the power of a good metaphor. Calatrava's overtly organic, derived-from-nature style is not Danny's thing, but he knows good architecture when he sees it, and he took the stand to say so. Not only had Calatrava adhered to his masterplan, he had enhanced it, he said. "It's a brilliant interpretation, and an inspiring one. Such a beautiful plan."

New York breathed a collective sigh of relief. There was, it seemed, to be no clash of egos here. No jostling between competing architects of the kind that had marked out the design of Freedom Tower, where Libeskind found himself unwillingly yoked with David Childs, the architect preferred by the site's developer Larry Silverstein. Instead, the city had been given a surprise present, a delicate crystalline object that somehow revived the spirit of the enterprise when it was clearly flagging. It was all very courtly. One can imagine it as a society play. After you, Danny, says Calatrava. No, after you, Santiago, dear boy, replies Libeskind.