Thermal Leggings
Thermal leggings/underwear are actually less useful than one might think, as whilst being very warm, they are completely impractical to take off when wearing overtrousers, harness, boots and crampons.
Bring one thin pair in case you get very cold weather on Mont Blanc for your week, but the combination of trekking and overtrousers is usually enough.
Quantity: 1 pair