Exhibitions are made for two main reasons: education and entertainment. Although I recognise the importance of education I am, by nature, a devotee of pleasure and want people to enjoy what they see in museums — not just feel that they must learn from it. Great exhibitions marry the two impulses effortlessly, and on balance the Vikings show, supported by BP, in the marvellous new Sainsbury Exhibition Gallery at the BM, is a great exhibition, though it does rather fall into two sections, the first somewhat more earnest than the last.