“Just a castaway, till your eye lands on me, oh!”

In my imagination, the discarded brown bottles of the city sing out to me. They want to be rescued. They want to be washed, scrubbed, cleansed, like seabirds plucked from an oil slick.

One day a friend asked me to brew some beer to sell, for charity, at her company’s Christmas fair. I said yes. I’d make a complex Belgian abbey ale, and a crowd-pleasing American-hopped IPA.

I had overlooked one major challenge, however. My stash of 330ml and 750ml bottles for the abbey beer was plentiful, but I was woefully short of the 500ml bottles I needed for my IPA, only two weeks before racking time.

I had three choices: buy brand-new bottles for the first time in three years; drink health-endangering, cellar-denuding volumes of beer; or go guerrilla.

I went guerrilla.

That was how I started collecting discarded brown bottles from the streets and gutters of London.

Usually these castaways are alone, not drowning but waving from their islands, their garden walls, their shadowy bus-stop nooks, their storm-drain crannies.

Occasionally, though, they come in swarms like heat-maddened ants on a humid August evening. Like the time I went for drinks on the roof terrace of the South Bank Centre, where a bar sold only Birra Moretti. As we left, snaking through a concrete maze to the exit and leaving the crowds behind, every table was weighed down with 10, 15, 30 empty bottles.

I filled my bags to overflowing.

The telltale scuffing on a Weizen bottle is the story of many careful owners, the wisdom of age, the privilege of taking countless fine beers from the brewer’s fermenter to the drinker’s table.

Many of the bottles that I rescue have been vessels for Moretti, or Budweiser. Perhaps a cheap Prosecco or cut-price supermarket champagne. Tossed on an impersonal tide of casual drinking, they are now washed up on the careless shore of crass consumerism.

Cleaned, their old labels scrubbed away, sanitised, gleaming, they transition to a new life of being filled, and filled again, with my carefully-nurtured brews. They are shared among friends and family, or settle in my cellar to bring rich and complex ales to maturity.

I believe this is what they call “upcycling”.

In his fairy tale, “The Steadfast Tin Soldier”, Hans Christian Andersen wrote about how a toy placed carelessly on a window sill falls into the street, is sent sailing away in a paper boat, and is ultimately eaten by a big fish.

The fish is caught, brought to market and sold to the mother of the child who first owned the tin soldier. She is astonished to find the toy as she prepares the fish for dinner.

The tale does not end happily, alas, at least when it is faithfully told. But it does make me wonder whether, one day, “by accident most strange”, I might hear one of my own bottles singing to me from the gutter, like the Steadfast Tin Soldier, or like a reply to the castaway’s message: “Despair not! Your call is heard! Your beer is drunk!”