1. Water pressure

Turn on every tap. Run them at the same time if you can. Low pressure in London flats usually means an old plumbing setup that will frustrate you every morning for as long as you live there. It can also indicate scale buildup in the pipes, which is expensive to fix.

2. The journey from the front door at street level to the front door of the flat

Time it. Count the stairs. Notice whether the communal entrance smells. Listen for noise from other flats. The thirty seconds between the front door and your flat is the part of the building you will use twice a day for years, and it is almost always invisible in the listing photos.

3. Window orientation and light at different times of day

Ask the agent which way the windows face. South and west are warm. North-facing flats can feel cold and dim even in summer. If you can, drive past or walk past the flat at a different time of day to check the light.

4. Sound

Open the windows. Stand still for one minute. Listen to traffic, neighbours, the building itself. Now close them and listen again. Single-glazed sash windows on a busy London road can be a deal-breaker if you work from home or sleep lightly.

5. The neighbours, audibly and visibly

Walk to each shared wall. Press your ear to it briefly. Look at the names on the buzzers. Check the state of the doormats outside neighbouring flats. London buildings have all kinds of residents and short-term tenants, and you only get a real sense of who they are by paying attention to small signals.

6. The exterior brick condition

Step back outside after the viewing and look at the building’s exterior. Cracked render, bowed brickwork, missing pointing, or staining around the parapet all suggest structural maintenance issues. Those become section 20 charges down the line.

7. Service charge history

Ask the agent to send the last three years of service charge accounts before you make an offer. If the agent says they can get them, that is a yellow flag. They should already be in the property pack. If they cannot get them quickly, that is a bigger flag.

8. The boiler

Look for the boiler. Note the brand, the model, and the date sticker if there is one. Ask when it was last serviced. Boilers in London flats are often hidden in airing cupboards or kitchen units. A boiler over twelve years old will probably need replacing soon (£2,500 to £4,000).

9. Damp patches in unexpected places

Look behind furniture if you can, especially behind sofas pushed against external walls, under bay windows, and inside built-in storage. Look at the ceiling in the room directly below the bathroom of the flat above (if there is one). London flats hide damp behind paint, and the agent’s photos are taken to flatter, not to inform.

10. Mobile signal

Stand in each room and check the bars on your phone. London buildings can have surprisingly poor signal even in central locations because of dense construction or steel-frame buildings. If you depend on mobile data and the signal is weak, your internet will frustrate you.

11. Storage

Open every cupboard. Count the storage spaces. Many London flats look great in photos and turn out to have nowhere to put a hoover, a suitcase, or a winter coat. If there is no built-in storage and no obvious place to add freestanding storage, you are about to live in a smaller flat than you think.

12. The bins

Walk to the bin store. Look at the floor. Notice the smell. Notice the gates and the access. If you cannot easily put rubbish out twice a week without trekking through the lobby in your pyjamas, you will resent it within a month. The bin area is also a useful indicator of how well the building is managed.