As their taxi approached Notre Dame and rolled past it, Mary described the cathedral's interior for Maria and David, then she said, "But it's far better to see it for yourselves. We'll visit tomorrow."

A while later, seated at a window table in La Tour d'Argent, they had another view of Notre Dame, though now the details were obscured in the fading twilight. As a waiter approached, Mary turned away from the view and said, "Because of the richness of the main course, we thought it best to begin with a clean, simple entrée." Then, looking up at the man, she continued, "Two dozen oysters on the half-shell and glasses of Champagne, please. And let the kitchen know we shall have caneton for four."

The waiter nodded and said, "Yes, madam. We have de Castelaine and Veuve Clicquot open."

"The Veuve, please."

"Ooh! That's exactly what David and I had when we came through to London before Christmas." Maria smiled and looked around the high-ceilinged restaurant and at the tall windows. "But the room was nowhere near as charming as this."

"Nor would it likely have had this background aroma." Michael chuckled. "As spacious and airy as the place is, they cannot prevent it."

David took another long, slow inhale, and after a pause, he shrugged. "Since we arrived, I've been trying without success to analyse what it is."

"It's our main course this evening, the restaurant's speciality." Michael paused and scanned the room. "And apparently, many other diners have chosen it as well."

"It smells both savoury and sweet. What is it?"

"Caneton Tour d'Argent. It's an old recipe from Rouen that Escoffier refined and elevated for the Savoy - Londoners took to calling it pressed duck. Here, they use the version straight from his cookbook."

A few minutes later, the platter of oysters arrived, and after the waiter had arranged the table settings and left, the sommelier took his place. As he poured the Champagne, he asked, "May I suggest a wine to accompany your duckling?"

Michael nodded. "I've thought to have an 1893 Hermitage. What have you?"

"I'm not certain, sir. With the collapse of demand for such wines, I've lost track of what remains in the older bins. Chapoutier, Chave and Jaboulet are regular purchases – or they were before the war, so we likely have '93s of each. I'll go check."

"Also, do you still have the 1911 Clos de Bèze from Domaine Ducroix?"

"Yes, there remains a good quantity, sir."

"Excellent. We'll have that as well."

After the sommelier left, David said, "Aha! An old Hermitage and a young Burgundy. This should set them on more even terms."

"It will to a degree, but we might need to have the Hermitage decanted immediately to allow it to breathe and soften further." He paused and shrugged. "Beyond knowing the wines themselves, we must learn how best to enjoy them - when to open them, whether to decant, in what order to serve them, what foods to pair with them, and so on."

"There's so much more to this than I ever imagined." David lifted his glass and watched the steady streams of rising bubbles, then he said, "This might be a good time for you to add to my knowledge and lore about Champagne. Wilhelm's conversion from beer and schnapps had been with bottles of it plundered after the capture of Reims. The way he described his surprised enjoyment showed me it was the wine he relished, not the conquest. He may have sought information about it."

"If he has learnt more, you can always defer to his knowledge and have him share it with you." Michael chuckled. "His being able to offer new information to you - the expert - should stroke his ego."

"True."

"There's no need to know everything about everything, David." He paused to take a sip. "But I'll provide more than sufficient for you to converse easily about most wines."

A quarter-hour or so later, while the oyster service was being cleared by a busboy, the sommelier arrived with three bottles. "Of the 1893, we have only the Chave and the Chapoutier, sir. The Jaboulet bin is now empty."

Michael examined the two bottles of Hermitage. "The Chave, please; it has the lesser ullage. And open it immediately, so I can assess whether it needs decanting."

"And decant this Clos de Bèze, sir? It's still rather young."

"No, we had the 1911 at the domain yesterday. It should be fine without decanting for our purposes this evening."

After a pleasant wait, a waiter wheeled a trolley to their table with the main course displayed on a silver charger. As their dinners were being plated, Maria asked, "Why is it called pressed? The slices appear normal, as do the drumsticks."

Mary chuckled. "No, those are removed along with the liver after the duckling is partly roasted. The remaining carcass is then placed in a screw press to extract its juices and marrow. The renderings are thickened and flavoured with the ground liver, butter and Cognac, before being added to the breast and legs to finish cooking."

"What gives the sauce its red colour?"

"Before roasting, the duckling is neither bled nor hung."

"Ah, that's why there's so much sauce."

While Mary and Maria discussed the recipe and the waiter continued arranging plates, the sommelier poured the wines into pairs of glasses at each setting. Then David pointed at them and said, "Impossible to mistake one for the other, isn't it? The Clos de Bèze is bright and the colour of wild strawberry preserves, while the Hermitage approaches maroon."

Michael lifted his glass of Hermitage, swirled it and brought it to his nose. "I remember this wine in its youth - deep red, hinting at black - and its tannins were so heavy that it was unpleasant to drink without many hours in a decanter. And even then, it lacked most of the nuances and complexity that have now developed."

He paused and shook his head. "Through my impatience, I wasted most of the quality in our bins of the 1893s by drinking them too young."

At the waiter's 'bon appétit', Michael looked up from his reminiscences. "Thank you. Yes, back to here and now."

After she had nosed and sipped her wines, Maria said, "They're both exquisite, but utterly different - in both bouquet and palate."

Michael nodded as he set down his Clos de Bèze and savoured the sip. "Indeed, and we'll find that each complements the duck in a different manner. We should begin, so we may determine which does it better."