One of a kind map

There's an interesting puzzle here. In effect, there are seven main areas of interest, which I'll take in turn:

The southern end of the 'Victoria line'. This was a real proposal, and its inclusion here dates this map to the very early 1950s. The Wimbledon branch of the District was in urgent need to relief, and it was perceived that this was more important than an extension of Route C (the forerunner of the Victoria line) towards Brixton and Croydon. The plan was to build a tunnelled line between Victoria and Fulham Broadway, and then share the District line tracks south to Wimbledon. A longer term proposal (when funds permitted) would then build the Victoria to Croydon section and use the Victoria - Fulham tunnel as part of another line (Route D) which would link Wimbledon with Chingford - a forerunner of the Chelsea-Hackney line. The stations that I've seen proposed for this section are Sloane Square and Chelsea; the four shown on this new map would be quite close together, which doesn't fit with the spacing ethos of the Victoria line. However, on a map they fit a sensible alignment along the north bank of the Thames, and if 'Fulham Road' is assumed to be around the junction with Finborough Rd/Gunter Grove (A3220) then the curve would align nicely with the District line tracks at Fulham Broadway. The latter was named 'Walham Green' in March 1952, so if we assume that the map is later than that date, I would posit that it is not very much later.
The 'Victoria line' between King's Cross and Finsbury Park. There was a lot of debate over the route north of King's Cross, and several routings to the west of Highbury & Islington, and the original Route C plan was for there to be no intermediate stations between King's Cross and Finsbury Park. A station at Barnesbury was mooted, but the main change came with the realization that by taking over the Northern City line platforms at Finsbury Park, and rearranging the layout with the Piccadilly line, cross-platform interchange could be provided. A similar rearrangement at Highbury would provide an easy route for Victoria line passengers to reach the City, and so by 1951 the view was tipping in favour of this route. This might seem to contradict the suggested map date in the previous paragraph, except that in 1953 the cost of providing the cross-platform interchanges were being challenged, and a suggestion was made to provide a more direct line between King's Cross and Finsbury Park, with one or more intermediate stations; the closure of Holloway Road and Caledonian Road on the Piccadilly line would allow a faster service on that line as well. The three stations shown on the new map are again rather closely spaced, and it is not clear where Islington would be placed. Liverpool Road might be the replacement for Holloway and Caledonian Roads though. In conclusion for this part of the map, taken on its own it would suggest a date of either 1947-50, or 1953-4.
The 'Victoria line' north of Finsbury Park. The station at Manor House was proposed in 1949, and by 1951 there was a suggestion that the Piccadilly line would be rerouted on a more direct alignment between Finsbury Park and Turnpike Lane, so that Manor House would be solely on the new line. Further east, the station of 'Walthamstow North' suggests that it would be to the north of the existing stations, although an alignment that encompasses Hoe Street (now Walthamstow Central) and Wood Street and links with South Woodford is quite reasonable. The original plan was for the line to surface at Wood Street, and it was only cut back to Hoe Street in 1961 in the face of rising costs. In the 1950s, continuing east to make an interchange with the Central line might have seemed sensible for the sake of another mile of double tunnel. What is strange is that I can find no record of such a proposal, and also that the stations in this section are notably more widely spaced than elsewhere on this map.
The 'Victoria line' in central London. Fitting in with the theme of more closely-spaced stations than were actually built, the 'Victoria line' on this map, there is an extra station at 'Bruton Street', between Oxford Circus and Green Park. I have never seen a mention of this, and it would provide very short inter-station distances in central London, keeping the line speed down. Further north, the line is routed via Great Portland Street, rather than Warren Street. This doesn't make sense on a map; it would force the line to turn sharply, which would again reduce the line speed. A plan from c.1950 shows the line curving more gently between Oxford Circus and Euston, but even this doesn't place it close enough to Great Portland Street. Warren Street was only added in the early 1950s, to improve access to this area and give interchange with the Charing Cross branch of the Northern line (the interchange with this branch at Euston was not as convenient as that with the City branch). The routing shown on this new map would suggest a date of no later than mid-1951.
The Bakerloo line extension. Given the likely date of this map, the Camberwell extension would have been foremost in the planners' minds. This was to have a station at Walworth Road, but this was shown on some plans as 'Camberwell Gate'. It was not until the 1960s that tentative plans for an extension that would take the line to Peckham and beyond were considered. The route on this new map initially makes sense: a southward path to Camberwell, where it would curve to the east under the A202 Peckham Road. Peckham High Street station would not interchange with any BR lines, but would be very central for the area. The next station is more of a problem though: the Old Kent Road is not on the alignment of the A202 between Peckham High Street and New Cross, and the line would have to make a northwards loop in order to serve it. I've checked an old A-Z, and it isn't even the case that the street names have changed. This looks like the artist has assumed that the Old Kent Road does continue south-east to meet the A202 alignment. However, this would then mean that Old Kent Road, New Cross Gate, and New Cross would be very closely spaced. A more sensible approach would be to have a station at Kender Street, and then a single station between New Cross Gate and New Cross with access to both. I can't make any conclusion on date from this extension.
The East London line extension. The East London line is extended northwards from Shoreditch to the Northern City line, via Liverpool Street. I'm not aware of such a scheme in the 1950s, and it would be a rather curvy route. Assuming that the main-line tracks to Liverpool Street would be used (the connection at Shoreditch was in place until 1966), one possibility is that trains would have to cross all the lines to use the former connection via Liverpool Street platforms 1 & 2, get onto the Metropolitan line, and then use a new connection to the Northern City (like that proposed by the Metropolitan Rly in 1913). This would miss out the station at Moorgate though. Alternatively, the line could enter tunnels north of Liverpool Street, have platforms below the main-line station, and then curve around to Moorgate. I can't see how the existing platforms at Moorgate could be used unless the tunnels made a 180-degree loop south of London Wall though. I can only conclude that this line is a fantasy, born of the connections on the Underground diagram making it looking easier than it would be in practice. At the north end of the Northern City, it is interesting to see a connection to the 'Victoria line'. The triple interchange ring suggests that new platforms could have been used for the Victoria line, which was almost never the case during the planning. At a real stretch this might suggest a date of 1953, when the cross-platform interchange plans were in doubt. However, the running connections would have incurred costs, so I struggle to see this as a sensible suggestion.
The base map. This is quite distinctive in that it is based on Beck's later 'almost rectilinear' map introduced in 1953. As you've almost certainly noted though, there are some significant differences. (i) The kink in the District line between Ravenscourt Park and Earl's Court; (ii) the west end of the Central line; (iii) the switching of the District and Piccadilly lines on the Hounslow branch; (iv) the south-east direction of the Wimbledon branch; (v) the Northern line south of the Thames; (vi) the east end of the District line; (vii) the Piccadilly line north of King's Cross (although this is clearly to fit the 'Victoria line' in).



In summary, the map appears to date from around 1953. The best evidence for this is that Fulham Broadway station is shown as such. Combined with the distinctive branching of the northern part of the base map, I don't think that it can be earlier. Some of the details of the 'Victoria line' mean that the date needs to be as early as possible, and show decisions that had been changed by 1953. This would suggest that the artist was not closely involved in the planning decisions at LT. Combined with the strange connection between the East London and Northern City lines, which smacks of playing 'join-the-dots' on an Underground diagram, my conclusion is that this is someone's fantasy map - but probably someone with some inside knowledge.