Flat 1, 23 Onslow Square, London, SW7 3NJ
About Flat 1
Flat 1 is a property in London (SW7 3NJ). It has council tax band G.
Held since February 2004 — that's 22 years off the open market, well above the local norm. 7 planning records sit against the property, 7 approved, 0 refused. Past consents include new windows, meaningful when judging how the property has evolved. The record references listed-building consent, which constrain future alterations. Across 1998–2004, sale prices on this property compounded at 9.4% per year.
Know exactly what you're buying at Flat 1
Before you offer, see what the listing won't tell you, the true value, the red flags and the full history.
Already flagged here
Launch offer · save £5
Valuation
against the asking price
Risks
planning & flood
Sold prices
similar homes nearby
Trends
the local market
Energy performance
No EPC on record
This property doesn't have an Energy Performance Certificate yet. An EPC is required to sell or let — and unlocks our automated valuation.
Planning history
Flat 1 has a listed-building consent on record — alterations to a listed property are tightly controlled.
- Sept 2025RenovationFullIn report
Replacement of 3no. sets of French doors at first floor front elevation with replica doors with slimline, double-glazed units. Modification of sidelights and overlights to accommodate slimline double glazing. (Retrospective application)
- Council
- Thurloe and Smith's Charity
RetrospectiveNew Windows- Documents
- 16 docs on file
- Reference
- PP/25/04313
- Sept 2025RenovationHeritageIn report
Replacement of 3no. sets of French doors at first floor front elevation with replica doors with slimline, double-glazed units. Modification of sidelights and overlights to accommodate slimline double glazing. (Retrospective application)
- Council
- Thurloe and Smith's Charity
RetrospectiveNew Windows- Documents
- 15 docs on file
- Reference
- LB/25/04314
We flagged 2 things worth checking at Flat 1
Independent checks surfaced things a buyer would want to understand before offering. The report explains each one in full, with the underlying data and what to ask.
- Signs of HMO activity in the area
- Larger development activity nearby
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Sales history & valuation
£1,050,000
Growth on file: 9.4% per year over 6 years.
Sales timeline
27 February 2004Most recent
£1,050,000
+69.4%over 5 years28 April 1998
£620,000
Median price across the last 5 sales in SW7 3NJ: £2,800,000 (2024–2022).
Nearby sales in SW7 3NJ
Flat 2, 23 Onslow Square, London, SW7 3NJ
Sold Nov 2024
£2,825,000Flat 12, 25 Onslow Square, Kensington And Chelsea, London, SW7 3NJ
Sold Oct 2024
£560,000Flat 11, 25 Onslow Square, Kensington And Chelsea, London, SW7 3NJ
Sold Jul 2023
£1,600,000Flat 3, 23 Onslow Square, London, SW7 3NJ
Sold May 2023
£2,800,000Flat 1, 17 Onslow Square, London, SW7 3NJ
Sold Aug 2022
£3,600,000
Everything we know about Flat 1, in one report
What it's really worth, what could be wrong, and the planning, sales and area data in full.
What we flagged
- Signs of HMO activity in the area
- Larger development activity nearby
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The neighbourhood at a glance
Rail-style transport is unusually close for this postcode.
Crime
10/mo
Rising year-on-year across the wider district.
Nearest stop
0.1 km
Onslow Square — bus stop.
Closest school
0.3 km
Oratory Roman Catholic Primary School. 58 schools nearby.
Go deeper on the local area
The full report breaks down crime, transport links, schools and air quality in depth.
Road noise across the postcode
Daytime· 07:00 – 23:00
58.4dB
Night-time· 23:00 – 07:00
48.1dB