A strange door at Holland Park
 

I was at the Holland Park station on the Central Line in Zone 2 today,
and I noticed a strange feature on the Westbound platform: across from
the platform, there was a large black door set into the base of the
curved trackside wall, with a handle and a large rectangular space cut
into the top. Looking into the suicide pit, I saw four large conduits
appear out of the platform side of the pit and disappear into the
other side of the pit right underneath the door.

Does anyone know what this door is?

Brad