The first rule of Puzzle Club: bring a rug, it gets chilly

Sometimes, I work in Wapping. At lunchtime in Wapping, your 'Things To Do' options hover somewhere between 'few' and 'limited'. This is why I often find myself in the St Katherine's Dock branch of Starbucks, reading an improving book or gazing out of the window, wondering what all the Bits – you can only really call them Bits – are that are floating in the water outside. During a recent lunch hour, I saw two older women at a nearby table, each doing puzzles from a newspaper. Here they are, in some superhero capes I drew on them, to represent their tireless and unswerving commitment to puzzling.

So there they were, riverside Rosemary and Thyme, one with the Express, I'm not sure about the other, maybe the Mail. Not talking, just puzzling in companionable silence. No "7 Across is a stinker today, Barbara"; no "Medieval instrument, 4 letters, something E something something. Any brainwaves?" Just quiet contemplation.

How nice to be with someone and not have to make conversation the whole time, as Harry says – or some variation of it – to Sally.

I am making a presumption, of course. It is possible that this was not the silence of contentment and friendship, but of steely competition. Of training.

Getting old is frightening. How long will you have your friends and loved ones around you? And how long will you have your faculties around you? And if you start to lose your mind, what can you do about it?

Not much, perhaps, but if you believe that keeping an active, engaged, exercised brain could make the difference between remembering the names of your children and not, you would probably go about pursuing the goal of cerebral fitness with the ardor of a person a third of your age.

Imagine if one of your pension-powered contemporaries started up some kind of subterranean puzzle club where, on a regular basis, you could compete in an aggressive, unflinching battle of wits, in a bid to keep your grey matter less, well, grey.

The stakes are high – your independence, your enduring powers of cognitive thought. This is why competition is conducted at the very highest level, and the secrecy of the location must be guarded by darkest oath. The last thing you want is someone who's proud of a half-completed G2 sudoku stumbling in to try their luck and wasting everyone's time. No one in that place has time to waste, and things would soon turn ugly.

Even if you should find them – if you follow the scent of freshly sharpened pencils, lavender and muscle rub like a bloodhound – you must say the password and answer a cryptic clue from the Times crossword in order to gain entry to their hideout.

Inside, a rickety table. Two comfortable chairs in a tiny carpeted arena, dingily lit by a flocked standard lamp. Maybe a footrest. A plastic magnifying sheet on a chain cast to the floor in triumph or bitterest frustration.

Maybe, post-bout, you might see an exhausted puzzler slumped in one of the chairs in a padded dressing gown, feverish with mental exertion, while their mentor pours weak orange squash over their head to cool them down - or warm-ish tea on a chillier day. You lose a lot of heat through your head. There's a constant low-level buzz – of battery-operated medical aids, and people murmuring the names of the canals of the British Isles under their breath.

Then, perhaps, there's a hush. The crowd part in reverence as the Wordsearch WarMachine shuffles into the arena. He is utterly fearless, even in the face of backwards diagonals, which everyone knows are the hardest.

If, like me, you enjoy a puzzle, you might be encouraged to 'age up', to infiltrate the competition, purely for the joy of puzzling. But you would soon get caught out when the sweat of intellectual endeavour causes the 'wrinkles' you've drawn on to your naturally lineless face with an eyeliner pencil to start running down your face. Or you lean back in relief at having completed a Codeword, only to leave a tell-tale silhouette of talcum powder on the headrest of the chair. It would be wrong to suggest you would be strong-armed out of there – there aren't many strong arms at Puzzle Club – but you might be jabbed in the thorax with a walking stick, or chased down by a mobility scooter. These people mean business.