The bay platforms at High Street Kensington

It's quite possible - relevant to this is that the line north from HSK, and the east side of the Cromwell Triangle, were built and owned by the Metropolitan Railway. There were no through District services (other than their joint operation of the Circle) until 1926.

I don't know if the District ever had any aspirations in that direction - the Met had the area of North Kensington pretty much sewn up as it already owned the H&C.

As originally envisaged, the District was intended to complete the Circle and provide connections from it to the West London Line at both Addison Road (Olympia) and West Brompton. (The Hammersmith extension came later) Hence the double triangular junction centred on Earls Court (High Street, Gloucester Road, Olympia, West Brompton). After the Great Falling Out the District went its own way. The bays at High Street (and the infamous Cromwell Curve) meant that it could keep its trains off Met tracks.

Geoff Marshall isn't allways the most reliable of sources

My bad regarding Geoff Marshall.

It does seem like consideration was given to extending the route northwards.

Perhaps being a pessimist here, but surely the only likely place they could have gone is onto a junction with the MR 'Circle' tracks north of HSK?

One can only speculate as to how useful or not it might have been to LT to have a four through track railway from before South Kensington to after HSK.

Fascinating. My Interest is with regards to any potential extension and separation of the High Street Kensington District branch route (possibility from Wimbledon), though AFIAK it is likely the case the original plan was for the proposed extension to eventually merge with the Circle Line tracks either prior to Notting Hill Gate up to Paddington.

Had the extended route managed to feature separate platforms from the Circle up to roughly around Bayswater, it would have possibly opened up more options on the discussion of separating this District line branch comes up down the road.