This cartoon by Christian Adams from The Daily Telegraph uses the concept of the Penrose stairs, an impossible object created by Lionel Penrose and his son Roger Penrose. The best known example of Penrose stairs appears in the lithograph Ascending and Descending by Dutch artist M. C. Escher, where it is incorporated into a monastery where several monks ascend and descend an endless staircase. (Source: Wikipedia)
In the cartoon, we see Barack Obama and Gordon Brown ascending/descending a Penrose staircase. A sign points towards 'Victory'. The rocky, mountainous terrain is clearly meant to represent Afghanistan. The never-ending stairs are a metaphor for the war in Afghanistan, from which there seems to be no way out for western forces.
FOOTNOTE
Just to prove that great cartoonists think alike, Schrank has an almost identical cartoon in The Independent on Sunday. Actually, I think Schrank's is the better of the two.
