MAY I BEGIN WITH A DASH OF HISTORICAL PERSPECTIVE? I DO SO AS A health warning, to myself as much as to anyone else. Just as the great Lord Salisbury once said that too much poring over maps tended to drive nineteenth-century ministers and military chiefs mad, an excessive concentration on prime-ministerial styles can propel scholars and commentators smack bang into the Tommy Cooper school of analysis – here you have collective cabinet government then, just like that , when the premiership changes hands, you switch to overbearing prime-ministerial government. There has been a good deal of this since Tony Blair entered No. 10 exactly 214 days ago.