Costa was busy with Christmas shoppers taking a break. There was just one small table empty, right by the window. I left Lena sitting there to keep the space, while I went off to join the back of the queue that stretched all the way to the door.

As I stood there, I watched her scanning all the other customers, a little smile on her face, lightly tapping her fingers on the table as she drank in the atmosphere. She was right in her element, in the heart of the action. Surrounded by strangers, but for Lena they were all her friends. Who’d have known that this woman was lost and confused just a few minutes ago? Who’d have known that yesterday she’d been handed a death sentence? Guilty of Alzheimer’s.

But I knew. I’d known about her illness for years. And yet I did almost nothing to help her until it was too late. Because I was an optimist, and I knew everything was going to turn out all right in the end, just like it always did for us.

I already knew on that beautiful summer day two years ago. Our girls had come to visit and we went to the lake for a picnic. We weren’t the only ones making the most of the sunshine. A group of runners — about 20 of them — were making their way around the other side of the lake. A few minutes later and they were thundering past on the lakeside path, going for it, bodies glistening with the effort. Lena pointed:

— Who’s that? What are they doing?

— Must be the local running club. Looks like they’re taking it seriously.

We went back to our sandwiches, fed a few ducks, uncorked a bottle. And then, a few minutes later, the running pack circled past us again, still not letting up.

— Who’s that? What are they doing?

— It’s the runners again. The ones who came past before.

When she had the same questions on their third circuit, I caught Josie and Annelie’s eye. Little frowns. Had mamma had too much to drink? Was she OK?

For them, this was new, but it wasn’t for me. For a couple of years now, I’d been noticing little changes in Lena. She’d always been amusingly scatty, occasionally forgetful — like the time in the early 80s on our first overseas trip together when she left her handbag and all our holiday money in a Paris restaurant. Of course it wasn’t there when we went back. But we were young lovers. What did we care about a little thing like that? 

But now it wasn’t just the morning hunt for the glasses any more. Lena would come up to the study where I was busy writing, and ask if I wanted a coffee. It never arrived. That bedtime book she was reading — it had been the same book for the past three months, and she kept asking me the meaning of the same word. And just last week, she’d been studying a course for the volunteer befriending work she was doing; she’d broken down in tears saying that none of the words made sense any more. This just wasn’t Lena.

A year back, I’d asked her to talk to her GP about her new forgetfulness. When she came back, I asked her how it went. She brushed off the question, and told me everything was fine. After the lake incident, I decided it was time for a second visit — and this time I’d go with her.

The GP was a formidable woman, someone who clearly had no truck with time-wasters. We had not much more than five minutes with her, and I quickly outlined my fears, explaining that Lena’s dad had been diagnosed with dementia in his late years.

— Yes, but your wife’s only 63. Most unlikely to be something like that at her age. But if you make a new appointment, I’ll run a few tests if that’s what you want.

So the next week she ran the tests — a series of simple mental agility questions: repeating a short list of words, counting backwards, identifying objects in a picture. When she’d finished, the doctor was stern with me.

— There’s nothing wrong with your wife at all. What you’re seeing is just the normal effect of aging. We all forget things — you probably will too before long. So I suggest you just show Lena a little more understanding.

I knew she was wrong. But I was a coward, afraid of the doctor, afraid of finding out the truth. So I did nothing. Hoping it would sort itself out. And now it was too late.

Outside our coffee shop, the sun had broken through and suddenly Lena, in her window seat, was golden. So beautiful outside, so broken inside. Perhaps only I could truly see her. Nobody else in the place seemed to have noticed her.

She was looking across the tables for me, near the front of the queue now. She found me, we locked eyes, and there was that special conspiratorial grin I knew so well:

— Just you and me. Our secret.

And suddenly I realised that nothing had changed. Lena today was no different from Lena yesterday, before the diagnosis. Our daily lives were still the same. Costa today was just like Costa last week — except a bit busier. We were still together, and probably would be for years. That’s what my research last night had told me:

‘On average, a person with Alzheimer’s lives four to eight years after diagnosis, but can live as long as 20 years.’

Lena wasn’t old. To my eyes she was still the dancer I’d met. She was fit, she was strong, she was healthy. So why shouldn’t we have another 20 years together?

I saw now that the consultant we met at the hospital yesterday had done us a favour: she’d given us a wake-up call, a sharp reminder that we’re not immortal. And since life has its limits then we should love every moment. Her diagnosis wasn’t a death sentence. It was a life challenge.

Finally it was my turn to be served.

— Yes, luv, what can I get you?

— A flat white for me. And … a hot chocolate.

— Do you want cream on the chocolate?

— Please.

— And marshmallows?

Yes. I’d make sure that from here on, Lena’s life would be full of little treats. Cream and marshmallows with everything.

I took the tray back to the table, laid out the cups, sat down, and reached across for Lena’s hand. She gave it, waiting for me to speak.

— I’ve been thinking.

— What about?

— We’re going to have an adventure.

— Ooh, are we going to the West Indies?

— That’s not quite what I had in mind.

But she’d remembered.

I remembered too. Stretched out on the bed together in my tiny apartment in Abu Dhabi. Still holding one another. Exhausted, but glowing. When was it? Our second day together, maybe our third. I knew her so little, but I knew everything. I knew already that Lena was forever. Crazy. I wasn’t looking for forever. Forever scared me, because I knew I was no good at it — hadn’t I screwed up a beautiful relationship once before? But this was different. I’d found a soulmate.

— What shall we do now?

— How about we go to the West Indies?

All those years ago, that’s where I’d promised her we’d go.