Newark-on-Trent, in the county of Nottinghamshire, was once the constituency of William Gladstone. It may be telling that when Gladstone entered parliament at the age of 23, he represented Newark as a conservative, with views which included opposing the abolition of slavery. He served as MP for Newark for 14 years, by which point his views were evolving.   The current MP for Newark, Robert Jenrick, took the seat in a by-election in 2014. His closest challenger was the UKIP candidate. Nigel Farage, then UKIP’s leader, had said he was tempted to stand himself, but instead the party put forward Roger…