I’m in the slow lane diligently doing the breaststroke. My fellow swimmers, mostly female, bob past me and perhaps adjust their stroke to give me more leg room. It’s an exercise in thoughtful choreography.

Then: bang! A midlife man hurls himself into the pool and indulges in a flashy butterfly stroke. We’re half capsized by the impact, water sloshing over our carefully arranged towels.

A midlife man hurls himself into the pool and indulges in a flashy butterfly stroke. We’re half capsized by the impact, water sloshing over our carefully arranged towels

Butterfly Man rips up and down the lane, unabashed as we scatter. With his head underwater no one else exists. Through sheer brute force, he owns the pool.

Manspreading — the art of taking up space on public transport by spreading your legs out — really is something that happens in water as well. Instead of emerging from the pool all zen and chilled-out, I leave the leisure centre white with fury.

I like midlife men, I really do. We have a lot in common. We worry about our waistlines, careers and shaky relationships. But gentlemen, as soon as you hit the pool, you become monsters. If you’re not carving us up in the slow lane (the clue is in the title), you’re hogging the shallow end, so obsessive lap counters like me can’t touch the side.

I seek out elusive women-only sessions (usually unhelpfully scheduled at 6am) and have even begged to join the silver class years early to no avail.

I seek out elusive women-only sessions (usually unhelpfully scheduled at 6am) and have even begged to join the silver class years early to no avail

So now I’m issuing new pool rules.

Gents, kindly refrain from butterfly or front crawl unless there’s no one else in the water. Be honest about the lane you need. And don’t stick your head down and ignore everyone.

A pool of swimmers doing steady laps is a beautiful thing. So don’t be an ugly blot on the landscape.