Saturday 11th November planned work

[sawb]

Can anyone shed any light on the nature of the planned work on Saturday 11th November, which will result in the Circle, District, Hammersmith & City, Jubilee and Metropolitan lines having no service on the whole line until 15:00 please?

[Dstock7080]

Metropolitan will be operating north from Harrow-on-the-Hill.
Other Lines until “13.10 for 4LM and Jubilee software update” is quoted.
A closure for SMA 8 testing will occur 2-3 December.