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56 Upper Montagu Street London W1H 1SN

25/09343/LBCListed Building Consent ApplicationApproved
Listed building consent

Approved on 13 August 2026

5 conditions

Site boundary (council red line)

Proposal

Use of ground floor and mezzanine levels to rear as residential (Class C3) use; deconversion of ground floor and mezzanine levels to rear together with two studio flats and one one-bedroom flat to form one three-bedroom maisonette; creation of reconfigured office unit in basement; replacement of all but one window with slimline timber double glazed units installation of secondary glazing to one window; renovation of shopfront; reinstatement of glazed fanlight with opening vent, new solid panel door, and awning; new glazed doors to south elevation of mezzanine garden room; new metal balustrading across rear boundary and raised terrace surface level with walk-on roof lights; replacement of concrete roof tiles with slate and new glazed roof light/ roof access; creation of green roof above mezzanine garden room; removal of modern partition walls and reinstatement of historical plan form as far as possible; reinstatement of historic period features all in connection with the use of building as office at part basement level with the remainder of the building being used as a single residential unit (Class C3) and associated internal alterations. (Linked to 25/09342/FULL)

Received
24 December 2025
Ward
Marylebone
Agent
Stratagem Planning Consultants Ltd.
  1. Received24 Dec
  2. Validated24 Dec
  3. Consult.
  4. Target18 Feb
  5. Decided13 Aug

Decided in 232 days (council typically 49)

About this application

This is a heritage application for an outbuilding at 56 Upper Montagu Street London W1H 1SN. Westminster has handled 2,677 applications of this type. This one was decided in 232 days, 26 weeks longer than Westminster's typical decision time. The site is in the Portman Estate conservation area, with 20 listed buildings nearby. There have been 2 other applications at this address. In the past year there have been 171 applications across Marylebone. We hold 896 applications in total for the W1H postcode area.

93% of heritage applications at City of Westminster were approved. Across all application types, the council typically decides in about 7 weeks (median).

Based on decided applications received in the last 3 years.Planning something similar? See what gets approved on your street

Application details

Postcode
W1H 1SN
Application type
Listed Building Consent Application
Scale / size
Small

Planning application dates

Date validated
24 December 2025
Target decision date
18 February 2026

Applicant and agent

Agent
Stratagem Planning Consultants Ltd.
Agent address
156 Camden Street London NW1 9PA United Kingdom

Planning decision

Statutory period
56 days

Additional information

Planning Portal ID
PP-14566426
Comments
0
Documents
21

Site constraints

Checking the site
2/3
Council recordsAppealsFlood risk

Designations that overlap or adjoin the site outline.

  • Conservation area: Portman Estate
  • Listed building: Grade II: 54, Upper Montagu Street W1On or next to this site · +2 more
  • Article 4 direction: Article 4 Basement Development Permitted Rights Removed
  • Flood zone 1: Low probability (rivers and sea)
Also checked, none recorded (21)

flood storage areas, tree preservation orders, green belt, scheduled monuments, World Heritage Sites, World Heritage Site buffer zones, registered parks and gardens, registered battlefields, Heritage at Risk entries, nutrient neutrality catchments, national parks, National Landscapes, SSSIs, Special Areas of Conservation, Special Protection Areas, Ramsar sites, ancient woodland, national nature reserves, local nature reserves, heritage coasts and brownfield registers.

A guide only, from official open data; it is not a planning search. Flood zones cover rivers and sea, not surface water.

Data © Crown copyright and others · sources and licences

Contains public sector information from planning.data.gov.uk (MHCLG and local planning authorities), licensed under the Open Government Licence v3.0. © Crown copyright and database right 2026.

© Historic England 2026. Contains Ordnance Survey data © Crown copyright and database right 2026. The Historic England GIS Data contained in this material was obtained on 2026-11-03. The most publicly available up to date Historic England GIS Data can be obtained from HistoricEngland.org.uk.

© Natural England copyright. Contains Ordnance Survey data © Crown copyright and database right 2026.

© Environment Agency copyright and/or database right 2026. All rights reserved. Flood Map for Planning, Open Government Licence v3.0.

Contains Ordnance Survey data © Crown copyright and database right 2026.

Source: Office for National Statistics licensed under the Open Government Licence v.3.0. Contains OS data © Crown copyright and database right 2026.

Associated applications

  1. 2025
    24 Dec

    Use of ground floor and mezzanine levels to rear as residential (Class C3) use; deconversion of ground floor…

    ApprovedFull Planning Permission ApplicationPart of25/09342/FULL
  2. 2025
    24 Dec

    Use of ground floor and mezzanine levels to rear as residential (Class C3) use; deconversion of ground floor…

    This applicationApprovedListed building consent25/09343/LBC

Source: Westminster

Contains public sector information from the Planning London Datahub, licensed under the Open Government Licence v3.0.

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