As an ad man he flogged us everything from the Tory party to condoms, but Charles Saatchi's most successful ongoing campaign must surely be his own brand of contemporary art. Now, he has installed his fabled collection in a permanent home just along the river from Tate Modern, filling County Hall's roomy 40,000 sq ft with works by artists whose names he has made, among them the Chapman Brothers, Tracey Emin and, of course, Damien Hirst, who is the subject of the gallery's opening retrospective.