A hotel in the 1940s a dance band Charity Wakefield as a high-class prostitute. Oh no, it’s not another Stephen Poliakoff drama, not so soon after Close to the Enemy! Is it? No, The Halcyon is more brisk and certainly more engaging even though you’ll feel you’ve seen it all before; it reeks of Downton Abbey and Mr Selfridge, with more than a sniff of Upstairs Downstairs.