The new Mayor of London, Sadiq Khan, said he wanted ‘the most transparent, honest and accessible administration London has ever seen’. It sounds lovely, especially if the Underground is cheap too.

Mr Khan’s are a very 21st-century triad of virtues, though honest might sound old-fashioned. It would once have appeared on a housemaid’s reference: ‘Diligent, sober and honest’, i.e. not lazy, drunken and thieving. We now grow sceptical of politicians who begin replies by saying ‘To be honest’ (as if this was a rare departure).

Honesty once measured outward respectability, as reflected in a Tudor description of Eton as ‘an honest Colege of sad Priestes, with a greate nombre of children’. Of course sad has changed in meaning too, meaning here ‘serious’. Zac Goldsmith did not play on his Etonian honesty during his campaign.

Terms of praise have an odd way of sliding. Transparent seems good, for no one in London’s City Hall must be a transparent rogue. But plausible was once seen as an equally good quality, attracting applause. The 17th-century Bishop Hall, who took possession of his cathedral in Norwich just as the Parliamentary soldiers had moved in, drinking and smoking their pipes, noted that Christ himself ‘came in a kinde, affable, and plausible manner’. He didn’t mean he was hiding anything. But 140 years later, when Edmund Burke wrote of the ‘plausible delusion of the hermetic art’, he saw nothing to be applauded in it. It was specious.

Yet to be specious was once praiseworthy. Another bishop, John Hacket, also applied this quality to Jesus Christ: ‘There is thy Saviour,’ he wrote of the Transfiguration, ‘looking like a specious Bridegroom.’ Such is the way of the world, that anything beautiful or specious on the outside must be untrustworthy.

Of Mr Khan’s triad of virtues, to be accessible is least transparent to me, honestly. In London it is mostly used of places possible to get into by wheelchair. It used to mean ‘open in character, friendly and approachable’. Boswell called Johnson ‘the most accessible and communicative man alive’. Perhaps it just means that Mr Khan will leave his office door open.