To learn about a leader, ignore their manifesto and just remove their constraints. Power reveals and absolute power reveals absolutely. It is an extreme way of getting to know someone, granted, but not too extreme for the British to try.
On June 9, the morning after the general election that she announced on Tuesday, Mrs Theresa May could be the most powerful prime minister since World War II. Mr Tony Blair was checked by a sullen chancellor of the exchequer. Mrs Margaret Thatcher had to reckon with trade unions that still mattered. Mrs May will have no comparable nuisances and, to believe the polls that give her Conservatives a lead almost equal to the Labour Party's entire vote share, the kind of majority that reduces Parliament to a formal imprimatur.
For the next seven weeks, Mrs May will try and fail to interest the media in her domestic reforms. This is a Europe campaign by another name, the first single-issue election since Mr Edward Heath asked voters to choose between his premiership and trade union power in 1974. And it should be: the terms of Britain's exit from the European Union (EU) are more material to the nation's future than any education policy or fiscal loosening.
Mrs May's victory will buy little to no leverage over the EU, which cannot allow the vagaries of national politics to cloud its interest in a tough exit for the United Kingdom. But it will push her political horizon from 2020 to 2022. She can now contemplate a longer transition from membership to non-membership, even at the cost of continued free movement of Europeans into Britain and a contribution to the EU budget. Any angry voters will have to wait years to punish her, by which time she may have retired to a nicer life of rural hikes and Ottolenghi recipes.
A vast majority would also allow Mrs May to pass whatever exit terms she secures through Parliament. It frees her from bothersome colleagues.
The question is, which ones? Some pro-Europeans assume that absolute power will reveal a moderate managerialist of a prime minister, an erstwhile Remainer who will shape a softish exit now that zealots to her right cannot block it in Parliament. Sterling's performance on Tuesday reflected this hope. Deutsche Bank has revised its bleak expectations for growth because, in part, an election will "dilute the influence of MPs pushing for hard Brexit".
If there is a limit to Mrs May's power after June, it will be Scotland... She must govern magnanimously to avoid provoking them to nationalism. It is not much of a constraint but it will have to do.
The trouble is that it will also dilute the influence of MPs pushing for soft or gradual exit. It will neuter MP John Redwood, the hardliner, but it will do the same to MP Anna Soubry, the inexhaustible defender of the Tory left. To assume that Mrs May is nearer to the second remains as durable a myth as her supposed indecision. Power might reveal a more thoroughgoing conservative than the markets realise. True, she is thought to oppose an abrupt exit without a trade deal or transitional arrangement, but so would almost anyone in her position. It is not much to cling to. It says nothing about the terms of the transition or the eventual degree of market access.
A very, very bad deal might have worse long-term consequences than no deal at all - and, as of June, it will be easier to pass. What really faded on Tuesday was not hard exit but the prospect of a reversal or dilution of last year's referendum. Until now, a pro-European could believe that Mrs May would agree to a deal too bad for Parliament to wear, necessitating a second attempt at negotiation under a new prime minister or an election fought on the question of whether to leave at all. That hope has dropped from faint to near-zero.
If there is a limit to Mrs May's power after June, it will be Scotland. Those who ran the successful campaign to preserve the UK in 2014 give some credit to Labour's poll lead ahead of the general election that was due the next year. Scots who disliked the Tories could vote for the Union in the hope they would only be governed by them for a few more months. Those voters can now expect large Conservative majorities in Westminster as far as the eye can see, starting in June. Mrs May must govern magnanimously to avoid provoking them to nationalism. It is not much of a constraint but it will have to do. The others expire in seven weeks.