To Starmer’s left, backbench rebels including Richard Burgon and Dawn Butler backed the push toward a customs union by the opposition Lib Dems. The members of the left-wing Socialist Campaign Group frame their argument around fears Labour will lose voters to other progressive parties, namely the Lib Dems, Greens and SNP, if they fail to show adequate bonds with Europe. Some other, more centrist MPs fear similar. Labour MPs with a military background or in military-heavy seats also want the U.K. and EU to cooperate further. London MP Calvin Bailey, who spent more than two decades in the Royal Air Force, endorsed closer security relations between Britain and France through greater intelligence sharing and possibly permanent infrastructure. Alex Baker, whose Aldershot constituency is known as the home of the British Army, backed British involvement in a global Defense, Security and Resilience Bank, arguing it could be key to a U.K.-EU Defence and Security Pact. The government opted against joining such a scheme.   Parliamentarians keen for young people to bag more traveling rights were buoyed by …