Homes in TW1 sell for a median of £700,000 across 482 sales over two years (HM Land Registry), which is -2% against the Richmond upon Thames median of £713,400. Set against the local average rent of £2,318 a month (ONS), that implies a 4% gross yield here versus 3.9% for Richmond upon Thames as a whole.
Rents are published per district, not per postcode, so the yield above applies the Richmond upon Thames average rent to TW1 prices. It's the right way to compare postcodes on entry price, but rents do vary street by street, and gross yield ignores costs, voids and mortgage interest.
TW1 averages tell you where to look, not whether one particular flat stacks up. Paste a listing and gemhome runs the actual numbers: yield, cash flow, the lender stress test, EPC work and what the public records say about that specific address.
Check a buy-to-let