London is a competitive market with a lot of demand in it. That combination is good news and it's also why the gap between a flat that's actively run and one that's simply listed is so wide here. Three things decide which side yours lands on.
It has to be priced, continuously. London rates move week to week: events, term dates, conferences, the weather. A rate set once and left alone isn't neutral; it's slowly leaving money on the table in the busy weeks and sitting empty in the quiet ones.
The busy weeks have to be caught early. A concert, a conference, a marathon, a bank holiday: the properties that earn well on those dates were priced for them weeks in advance, not on the day. That's the difference between a good month and an ordinary one, and it's almost entirely a question of paying attention.
And the property has to be sold to the right people. A flat near a tourist attraction, a flat in a business district and a flat near a large project or hospital are three different products, even if they look similar inside. Different guests, different lengths of stay, different booking behaviour, different platforms. The listing, the photos, the minimum stay and the channel mix should all follow from which one yours actually is, and most listings are written as though every property is the same one.
None of this is difficult in isolation. All of it, every week, alongside a job, is why most self-managed London flats run well below what they're capable of.