London Gatwick (LGW): Thameslink & Southern Beat Gatwick Express
Skip the expensive Gatwick Express (£21.50+) unless you want Victoria nonstop. Instead, tap in with Contactless on Southern (32 min to London Victoria, £10.10–£15.90) or Thameslink (30 min to London Bridge, 38 min to Blackfriars, 45 min to St Pancras International).
London Stansted (STN) & Luton (LTN): Contactless Warning!
Crucial rule: TfL Contactless bank card tap-in is NOT valid on Stansted Express beyond Tottenham Hale — you must buy an e-ticket online (£9.90–£23) to avoid a £100+ penalty fare at Stansted Airport gates. At London Luton (LTN), contactless works seamlessly across Thameslink + the automated Luton DART shuttle from St Pancras in 32 minutes.