Charing Cross to Higham

Carrying on from my question on Smithfield Sidings in the 2004 era in the WTT covering the North Kent simulation I have noted there was a service from Charing Cross to Higham. I know the sim has not got an era that early however having a look at the Higham Layout on the sim and it shows exactly the same as the Quail maps for both 1994 and recent layouts and there is no turn back possible at Higham.
Does anyone know if there ever was temp workings at this time that allowed this frequent service to run with only a 10 minute turnaround as shown in the relevant CWM I have looked at.

Yes that is correct about the tunnel lining. Prior to that, Both Strood & Higham only at brick work at the Tunnel mouths and several yards into the tunnel. The rest was just carved out chalk. Originally the tunnels where one tunnel excavated by the Thames and Medway Canal Compnay long before the advent of railways.A major collapse occurred and that was how there are now two tunnels. There used to be "Tunnel Watchmen" who had to walk both tunnels several times a day to watch out for chalk falls. And they were very common. The tunnels were quite wide before the lining, and you could walk the cess in the tunnels with trains passing. In my Permanant Way days, I had many a job to do in these tunnels. Midway in Strood Tunnel it was like the inside of a huge cathedral formed from subsequent chalk falls. At the Strood end there used to be a dock which was were the original canal joined the River Medway. Developers came along and filled it in ready to build on it. What wasn't realised, the dock acted as a drain for the tunnels after they were filled to run the railway. Consquently both tunnels suffered from flooding. An array of diesel traction was used because the third rail was unuable at the time, to shuttle passengers through the tunnels until a solution was found.