Disco TD5 High Beam warning lamp failure

Hi all. Had my Disco in for NCT (MOT) equivalent here in Ireland and it failed on the Headlight High Beam warning lamp on dash, among a few other small things. I stripped the binnacle yesterday to change the bulb but it didn't illuminate. I put a test meter at the 2 contact points on the circuit board and have established that I am not getting voltage when high beams are switched on. Headlamps are switching fine but the warning lamp doesn't appear to be getting power. Is the warning lamp operated by the BCU where an earth path is created or is it just a relay or something that sends the signal?

Thanks all....