{On the granite plaque, on the right hand side, a crest headed:}
Metropolitan Borough of Chelsea
{on the left hand side:}
Erected 1906-8
W. J. Mulvey JP - Mayor 1905-6
Hon. W. Sidney JP - Mayor 1906-8
Maj. W. F. Woods JP - Chairm. of Comtee.
Thomas Holland - Town Clerk ES
We found a few things about Holland, even a photo, but we cannot explain the 'ES' which we have not seen before after a 'Town Clerk' on plaques with similar wording (and they are quite common).
The plaque commemorates the extension to the Town Hall, including this whole elevation.
Site: Chelsea Old Town Hall & Smedley (2 memorials)
SW3, King's Road
The two plaques are at the centre of the frontage behind the bike stands.