Legal changes to Britain’s deal to leave the European Union will be difficult but recent trips by British ministers to Brussels have been productive, the prime minister’s effective deputy, David Lidington, said.

“It was a very useful discussion about the politics, both within the United Kingdom and within the EU27, and a scoping out of what was possible. Reopening the withdrawal agreement... will be very difficult,” Lidington, who serves as Cabinet Office minister and was in Brussels last week, told.