Serious is the word that sums up Vince Cable. He has got a sense of humour, as we know, but when he's talking economics he cannot help but be a touch austere, dour even. Mr Cable is very serious, for example, about finding yet more economies in public spending. One new suggestion he makes is that the age qualification for the winter fuel allowance could be raised to 65, though payments would be extended to the seriously ill and disabled; this would yield a net saving of 250 million pounds. Another idea, in keeping with Liberal values, is to abandon the next generation of biometric passports and the ID card scheme.