“he and Sophie hurdled a turnstile at the Temple tube station and dashed deep into the grimy labyrinth of tunnels and platforms.”
There aren’t any turnstiles – there are electric barriers opened by a ticket, but I’d like to see anyone hurdle them, they’re big*. It would be possible to climb over them with difficulty, but what about the London Transport officer whois always present? And how did they get out they other end? Hurdled again? (The barriers have to be passed through each end of the journey). Why didn’t they buy tickets? Langdons got a credit card he could get cash with at a cash machine (ATM)
That part of the underground is not the tube (its forgivable mistake –the tube is the deep underground lines with the small trains and round bore tunnels), this is a cut&cover wide tunnel running immediately below the road surface. Temple station has two platforms (east & westbound) and one short (about 30 steps) staircase down to each. No labyrinth, not deep.
But where are they going anyway. Brown doesn’t say what their destination station is, but if they’re going to Kings College, then that’s next door to Temple Station, and the entrance is in the Strand – a road they’d have to walk down to get to Temple station.
Go to www.streetmap.co.uk
and enter postcode WC2R 2PH – that centres the map on Temple station. You’ll see Kings College to the immediate left – the green block marked ‘coll’ and Somerset House and Fleet Street (where they’ve come from) above it.
* here's a pic of the underground barriers