I’ve actually thought for a bit and realised that instead of using East Midlands Railway, we should use Greater Anglia smart card as a Travelcard carrier instead!
From their website/app, set a journey from Brentwood to Liverpool Street departing in morning rush and then select the Travelcard option, then you can get an Anytime Zone 1-9 Travelcard on a smartcard costing £25.70 w/o Railcard discounts.
