In The Cage , everyone is trapped. They are weighed down by debts and obligations, by family and friends, by work and duty. They twist and turn, and, with each manoeuvre, find themselves beating against the walls of their prison. In its glittering Merseyside setting, The Cage , a new five-part crime drama on BBC One, demonstrates the enduring appeal of breaking out of the confines of your circumstances. The Envoy is a downmarket casino in Liverpool , where punters play blackjack deep into the night – and long after their pay packet has protested. Matty (Michael Socha) works on the floor, keeping an eye on the luckless degenerates who frequent the place, while Leanne ( Sheridan Smith ) gets glammed up and heads for the cage, where money is exchanged for chips, the native currency of the gambling industry. Both, however, are skimming a bit of cash from their employer. A hapless endeavour, and one that puts them at risk: the casino is actually a money laundering operation for a drug empire.…