The park's rule is simple: climbers must be at least ten years old to attempt the summit. Our view, from watching families on the mountain, is that the comfortable sweet spot starts around twelve: old enough for the walking days, old enough to communicate clearly about how they feel, which matters enormously up high, and old enough to bank the achievement as a permanent part of who they are.

There are two schools of thought on climbing a mountain with the person you love. One says it is the most romantic thing you will ever do: a shared summit, a sunrise nobody else will ever fully understand, a story you get to keep telling together for the rest of your lives.

Let me declare an interest immediately: I climbed Kilimanjaro as a middle-aged man doing something his knees had opinions about, and I wrote a whole book admitting it. So when someone in their fifties or sixties asks us, usually quietly, usually at the end of an email about something else, "honestly, am I too old for this?"

Over the past weeks we have compared Kilimanjaro, honestly, one mountain at a time, with the seven great treks and climbs it shares the world's daydreams with: Everest Base Camp, the Inca Trail, Mont Blanc, Elbrus, Aconcagua, Mount Kenya and its neighbour Meru. Every one of those pieces answered the same question: this one, or that one?

The final comparison in this series is the closest to our hearts, because these two mountains share a horizon. Mount Meru stands barely seventy kilometres from Kilimanjaro, close enough that from Meru's summit ridge at dawn you watch the sun rise directly behind the Roof of Africa, floating on the clouds across the plain.

Africa's two greatest mountains stand a border apart, and the comparison between them is the connoisseur's favourite, because it is the only one in this series where the quieter, lower, cheaper mountain has a genuine claim to being the more beautiful.