A couple of comments - I wouldn't say any London council was full of "left wing nut cutlets" these days. We've moved on a long way from the worst excesses of the 1980s. It is quite clear that traffic levels in the centre of town are lower than before and TCR is in the congestion charge zone.
I would point out that Boris has been in charge when most gyratories have been removed or remodelled and more are on the way. Trafalgar Square was Ken's big scheme but it is Boris who's continued the trend. Although this is a Camden scheme it is in line with the Mayor's strategies just as the Piccadilly 2 way scheme, that Westminster City Council did, was. Tottenham Hale is the latest one with Aldgate, Vauxhall and Elephant and Castle to follow.
I think there is a bit of a "fashion" in traffic planning to remove gyratories just as there was in the 1960s to create them! My own view is that its not yet clear whether the end result justifies all the expense. I'm certainly not convinced by the T Hale gyratory removal as it seems to have slowed everything down and people still drive down Broad Lane despite the main flow being via different roads!
The Tulse Hill gyratory system is also apparently set to change too though with £5 million earmarked for improvements, some of which should be implemented by Christmas.
EDIT: just found a small summary of the changes for the 17 junctions that will be upgraded:
Croydon Fiveways – Major work to reduce traffic congestion in the local area and support growth in Croydon's metropolitan centre
Balham High Road (Balham Boulevard) – The Balham Boulevard scheme will provide improvements to support the Balham Boulevard project including better pedestrian and cycling facilities and investment in public realm, including the planting of new trees
Brent Cross/Cricklewood – Creation of a new road layouts and public spaces in the area to support new development and improve access to retail, dining and leisure facilities
Charlie Brown's Roundabout – Improved facilities for pedestrians and cyclists, including new signal controlled crossings
Euston Road – The creation of better crossings for pedestrians and cyclists, improvements to the local environment and work to support the movement of buses and other road users along Euston Road
Lombard Roundabout – Major improvements to the operation of the roundabout and the creation of better facilities for cyclists and pedestrians
London Road Roundabout – Improvements to the roundabout, including facilities to make it safer for cyclists travelling through the area
Malden Rushett – Wider improvements to the A243 Leatherhead Road junction with Rushett Lane and Fairoak Lane, including a big focus on road safety and installation of new pedestrian crossings
Mill Hill Circus – Work to reduce congestion and improve journey time reliability in the area
Purley Cross Gyratory – Improvements to the the quality of public realm and better access through the area for bus passengers and other road users
Renwick Road (Barking Riverside) – Safer access for road users, including pedestrians and cyclists, to the Barking Riverside development from the A13
Seven Sisters Road – Woodberry Down – Scheme to deliver safe, reliable and accessible road improvements to support new housing development in the local area
Stoke Newington Gyratory – an upgrade of the existing road layout to make it safer and more easier accessible for pedestrians and cyclists
Thornton Heath Ponds – Focused on improving the quality of public realm around Thornton Heath Pond
Trinity Road/Burntwood Lane – Work to reduce congestion and delays at the junction of Trinity Road and Burntwood Lane
Tulse Hill Gyratory – Shorter-term scheme to improve road safety ahead of a longer–term scheme to address concerns about the operation of the gyratory
Victoria Circus – Improvements to the local area for pedestrian and cyclists to support the major upgrade at Victoria Station.