Caricature has been alive and well since the 17th century and especially since Hogarth’s time. That’s a message that comes over loud and clear in the Tate’s Rude Britannia exhibition (June 2010). There’s an attempt to divide into sections – bawdy, absurd, political, social satire – but the simpler characterisation is political and social.

Punch defined a century of British life (I loved Charles Spencelayh’s Laughing Parson, chuckling over his copy of Punch), and Lee Baxendale lampooned all our schooldays brilliantly with the Bash Street kinds. Viz took us places where DC Thomson no longer could.

But even Viz, thirty years on, seems quite gentle and playful. Political caricature isn’t. Buttocks and wind featured large for Gillray and Rowlandson, with royalty the very literal butt of their humour. Nothing quite so blatant these days. Spitting Image, Scarfe and Steadman stand out. Martin Rowson too. Tony Blair is a godsend: few have fallen so far, and few have a smile and a gauntness that gives so much help.

On the downside there are sketchy contributions from the likes of David Shrigley which are for the most part facile and tell us nothing. Sarah Lucas has a depressing self-assurance, and short films try patience. Caricature is all about immediacy. As with satire there’s a strong intelligence that characterises the best, a relevance and impact, a stretching of truth that nonetheless never loses touch with reality.

Talking of stretching – there’s Major’s stretched underpants, Blair’s stretched smile, Robert Walpole’s stretched buttocks. You don’t have to stretch to much, a nose here, a jawline there, and that’s enough. Scarfe and Steadman went further of course, but they’re exceptions.  For both satire and caricature it’s the little push, the little stretch that pays the biggest dividend.