He and I are in Madeira on an adventure-packed week with Traveleyes, a specialist in holidays for visually impaired people (VIPs), which has an ingenious modus operandi — offering sighted travellers hugely discounted trips to act as guides and eyes for the VIPs.
Our group is eight VIPs, 11 guides and a Traveleyes tour manager, Caroll, who cuts mean deals in restaurants and pairs us with a different partner each day.
Madeira, a ravishing, natural beauty, often called the pearl of the Atlantic, is famous for its flowers and exotic fruits. When we arrive, it's decked out in the dazzling colours of spring, its rich, volcanic soils giving up purple and white agapanthus, orchids in peaches and cream and rhubarb and custard, hydrangeas in blue and pink and trees heavy with angel's trumpets, jacaranda, mimosa and flames of the forest.
The VIPs can't see any of this, so we head to Funchal's food and flower market to discover the exotic plants and fruits through our other senses.
Even on a busy day the stallholders are unfazed by us, handing out their wares without hesitation. Touch, smell, taste — I use these senses constantly, generally on auto-pilot and mostly simultaneously, but standing in the market I try to isolate them, concentrating on one sensory experience at a time.
I feel the soft velvet of a petal; the waxy, almost plastic head of a flamingo lily; breathe in deeply to take in the delicate spicy scent of an orchid, and keep the creamy morsels of the monstera fruit — part-banana, part pineapple, wholly amazing — resting in my mouth a while before swallowing.
I expect VIPs to be able to taste, smell, hear better than I can. Sue, who lost most of her sight through diabetes 16 or so years ago, says that's simply not so.
"I really don't think my other senses have improved to compensate," she says, "but what has happened is that I concentrate more on listening, on eating, on what's going on around me.
"We all rely so much on sight, and when that goes, you're left feeling very vulnerable. So you have to use your other senses to the max to keep yourself as safe and independent as possible."
Independence is key and guides are given some essential tips on how to accompany a VIP. Most of the people I escort prefer contact, so we walk arm-in-arm exploring levada trails — mini canals — scented gardens and quiet seaside towns.
All the while, I'm looking out for hazards — low branches, uneven footpaths — and describing what I see. I'm not often lost for words, and yet on these walks I find myself struggling whenever I have to strip my commentary of colour for those who've never known the joy of seeing blue, or green, or purple, or any of the six million hues someone with healthy eyes can detect.
Take my walk with Leslie through Levada da Serra do Faial, also known as Paradise Valley.
Leslie's been blind since birth and has no concept of colour or awareness of light or dark.
My descriptions of dappled forests, of deep green valleys, of hilltop village houses with red-tiled roofs, of patchwork, terraced vineyards, don't enhance her experience by very much, so instead we amble along in companionable silence, listening to the birds while she picks out the notes of the Madeira blue chaffinch and blackcap and teaching me to do the same.
We stop often to place our hands around huge-headed agapanthus, to run our fingers through the cool, quietly gurgling waters of the levada, to catch the sound of the breeze in the trees and to listen out for lizards scuttling this way and that in the undergrowth.
And we talk: the physical intimacy of linking arms breaks down our British reserve and accelerates the rate at which we jump from pleased to meet you to more personal matters, namely my latest dating disasters.
"Well I suppose that's one advantage I have over you," says Leslie. "When I met my husband, I fell in love with him, not his appearance. You sighted people, you're so shallow ... "
Next day I'm paired with David, Leslie's husband, for our longest, most arduous and exhilarating walk, to the top of Madeira's highest mountain, Pico Ruivo. It's a fantastic trek, winding up narrow precipitous paths with don't-look-down jagged plunges.
I climb first; David follows closely behind, his left hand resting lightly on my shoulder, his cane in his right. I guide him along, warning him of loose stones underfoot, broken paths, tree roots, shallow steps down, deep steps up, until we reach the 1800m summit, high above the clouds.
The panorama is spectacular, with hulking volcanic masses set against vast, intensely blue skies, but what makes this one of the most rewarding and memorable experiences of my life is David's joy at our achievement.
On the way down, we stop at a pop-up stall to drink poncha, the local hooch made from sugar cane rum, and David tells me that I and the other guides have no idea of the gift we give VIPs when we travel with them.
From where I'm sitting, I've gained at least as much as he has. I feel I've had an amazing time with a great bunch of people.
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