The race to succeed Angela Merkel as the leader of Germany’s ruling Christian Democrats (CDU) is on a knife-edge, as the final stages of the leadership contest re-open ancient political divisions among the party’s old guard.

Some 1001 party delegates will gather in Hamburg on Friday for a series of votes to elect a new party leader, who will instantly become odds-on favourite to be Germany’s next Chancellor and the leader of Europe’s most powerful economy when Mrs Merkel retires.

The contest, triggered after Mrs Merkel announced she would not stand for re-election following a series of poor election results since the 2015 migrant crisis, has exposed ideological and personal splits in the party…