This is genuinely harder to judge by eye than it sounds, because "what a healthy dog looks like" varies enormously by breed — a number on a scale means very little without knowing what that specific dog's frame is actually built for. A vet's proper assessment is the real answer here; what follows is general awareness that helps frame that conversation, not a replacement for it.

The rib-and-waist check

A commonly taught, genuinely useful home check, generally known as body condition scoring in more formal terms: you should be able to feel your dog's ribs fairly easily without pressing hard, and see or feel a visible waist — a tuck-in behind the ribs — both from above, looking down at the dog's back, and from the side. No easily felt ribs at all usually points one way; ribs and spine both very prominent with no covering usually points the other. This isn't a replacement for a vet's actual assessment, but it's a far more useful home check than weight in kilos alone, precisely because it adjusts for the dog's own frame automatically.

"He just has a big frame" is sometimes true, and sometimes a story

Breed size genuinely varies enough that comparing one dog's weight number to another's tells you very little. The rib-and-waist check cuts through that confusion in a way a number on a scale can't, which is exactly why it's worth learning to do rather than defaulting to a number that was never really specific to your dog's actual build.

The London-specific pattern worth naming honestly

Pavement treats, a bite of something at a dog-friendly cafe, and well-meaning strangers feeding a friendly dog mid-walk all add up in a way that's genuinely easy not to track — none of it feels like "feeding" in the moment, and all of it counts the same as anything measured out at home. Worth being honestly aware of, especially for a dog that spends a lot of time out and about meeting people.

Why this is a trend question, not a single-meal one

Weight tends to shift slowly, over weeks and months, rather than as the result of any single day — which is exactly why a single indulgent afternoon isn't the thing to worry about, and a consistent pattern is. This is also why a steady daily walking habit, rather than one occasional long effort, is the thing that actually helps over time: small, regular walks that reliably keep happening do more for a trend than one big correction ever does.

If there's real uncertainty after an honest rib-and-waist check, that's exactly the kind of specific, quick question worth taking to a vet rather than sitting with — it's a genuinely common question, and a fast one for a professional to actually answer.