Their business-savvy mentality stretches far beyond sex work, having launched themselves to international stardom with their documentary portrait Meet The Fokkens (2011), followed by three memoirs, DVDs, an imminent foray into music, and the promise of more to come (ahem).

The twins meet us out front at the oldest church in the heart of the Red Light and start at the beginning. It’s the 1960s: the sexual revolution was abloom in the city, donning sexual independence and miniskirts. The district was known for sex work from as early as 1500, but that remained discreet and hidden up until the 1950s, and come the Sixties, window- fronted brothels, revealing outfits, and sex shops were popping up like wildflowers.

We stroll through the red glow of narrow alleys, past wafts of weed smoke, and make our way to the canal-side of one of the city’s oldest streets (Oudezijds Voorburgwal). We’re standing outside the building where it all began for Louise. The year is 1961, Louise is 19 and married with three children to Wimpie – a hotshot bodybuilding, karate-training barman. His friends had a room available, and the rest is history. “My head was in the clouds the first time, but it went well. I started earning money for the family, but Wimpie was driving a [Ford] Thunderbird in no time.” She started hiding her money from him after that.

Sex work was a way of earning a living in post-war Amsterdam and paved the road to independence for the twins. “The brothel owners tell you: you have to work for something; not just drinks and clothes. A lot of women buy a café, a market stall. I bought a house with Wimpie. That’s the way.” Two years later, Martine joined the trade. Since then, they’ve entertained “everything under the sun” from priests to doctors, to offering light beatings and doing threesomes together. “Why not? It was fun!” In the years that followed, the sisters eventually earned enough to go independent, owning and running their own brothel and founding the first informal trade union for sex workers, Het Rooie Lichtje (‘The Red Light’).

“De Wallen has lost its romance,” bemoans Louise. The Red Light used to be a village, guarded by social control. “Now it’s lost its soul.” Local government has been intervening heavily in the past ten years, driving out criminals and injecting capital to incite gentrification. “Hell’s Angels kept the balance. If there’s a rotten apple, you need to get them out.” There was always someone watching the house, and if they ever encountered an aggressive client, all the girls would help kick him out.

Gently taking my arm as we saunter, Martine explains the games involved in her line of work: “You ask a certain price for them to come inside, and then later, you can try asking more. It’s a game – life is a game.” Weighing in on the ethics of pricing, Louise divulges: “There’s no limit, but if a man has a lot of money, you don’t take everything. You leave him with enough for a beer and a taxi home.”

We meander past renowned sex shows and historic monuments, stopping on another street corner where they once worked. The sisters show me how it’s done, throwing out charms to lure in passers-by. “Hallo, come inside, honey, we make a nice time. Hi, young man. We can still have fun.”

Against the backdrop of the broken-up canal – the charming chaos natural to the downtown neighborhood – the twins gleam in smiles with pride and excitement for the future. As our time together comes to an end, they break into song to serenade me.

“When the curtains close, we’ll make men fall, then we sure will have a ball. Happy men will always leave our door, ‘cause they all come back for more. And when the curtains open up again, then we sure did a good job. And if all was well to your delight, come to the sisters at the Red Light, come to the sisters at the Red Light.”

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