Tested and works fine.
Hornby R8082 HM 4000+ Left DC Controller Slave Add-on Unit For HM2000 & HM4000
Hornby R8082A HM4000+ Add-on Right Hand Controller for HM4000 & HM2000
Hornby R8081 HM4000 Twin Track Controller With Brake N & OO Gauge
HORNBY HM4000 POWER CONTROLLER PLUS 2 x HM4000+ SLAVE UNIT CONTROLLERS