Flat 1D Block 1 Portman Mansions Chiltern Street London W1U 5AJ Data via plota.co.uk
Proposal
Replacement of existing single-glazed timber sash and casement windows with double-glazed timber sash and casement windows to match the existing style and opening type. Existing window frames to be retained with no changes to the structural openings. Data via plota.co.uk
Application progress
Refused on 17 Oct 2025 · Delegated Decision · Last checked 18 Oct 2026
Documents 13
Decision & officer reports 2
Statements & assessments 2
Plans & drawings 2
Application forms 1
Consultation & comments 1
Other documents 5
Site constraints 10
Show all 6 with distances
- 30 m13, Allsop PlaceGrade II
- 72 m94-114,118 to 124, Baker Street W1Grade II
- 91 m78, Chiltern StreetGrade II
- 111 m105-115, Baker Street W1Grade II
- 145 m2, York Street W1Grade II
- 147 m47, YORK TERRACE WEST NW1 (See details for further address information)Grade I
Checked on 2 November 2026. Historic England, the Environment Agency, Natural England, the Planning Inspectorate, Transport for London (public transport access levels, Powered by TfL Open Data, OGL v3.0, contains OS data © Crown copyright and database right 2025) and council datasets, Open Government Licence. A boundary can run through a site and the council holds the definitive record: confirm with the council before relying on this.
Building
From the energy performance certificate lodged in November 2008, the latest held for this property. The building may have changed since. View the certificate
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Important details
- Council
- Westminster
- Application type
- Full Planning Permission Application
- Postcode
- W1U 5AJ
- Received
- 19 Aug 2025
- Validated
- 1 Sept 2025
- Ward
- Marylebone
- Case officer
- Show
- Target decision
- 27 Oct 2025
- Decision
- Application Refused
- Decision date
- 17 Oct 2025
- Decision level
- Delegated Decision
- Applicant
- Show
- Agent
- Design Extension - https://www.designextension.co.uk/
How this decision compares
Decided in 46 days from validation, 30 days faster than Westminster's median of 76 for full applications. Refused, as 14% of full applications here are.
Plota live figures for full applications decided by Westminster in the last twelve months, from validation. Westminster decision record →
Public comments
No public comments yet.
27 neighbours consulted · Last counted 18 Oct 2026
Consultation & key dates
- Alt. reference
- PP-14259976
- Planning Portal ref
- PP-14259976
- Comments by
- 8 Oct 2025
- Site or press notice
- 4 Sept 2025
- Env. assessment
- No
Historical activity at this location
25 nearby applications on record - archival context, not part of the live application.
Nearby activity
Westminster is slower than most councils at deciding householder applications, ranking #258 out of 296. Only 28% of applications have the time limit extended, well below the 41% national average - the council usually decides on time. Westminster is also one of the strictest councils - it refuses more householder applications than almost any other, with only 81% approved vs 90% nationally.
Freehold boundary: © Crown copyright and database rights 2026, HM Land Registry. Polygons © Crown copyright and database rights 2026 Ordnance Survey 100026316. Conditions of use
Energy performance: Energy performance certificates from the Energy Performance of Buildings Register, Ministry of Housing, Communities and Local Government. Contains public sector information licensed under the Open Government Licence v3.0. © Crown copyright 2026.
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Flat 1D Block 1 Portman Mansions Chiltern Street London W1U 5AJ
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