[1] Their parents' financial support allowed them to maintain a household of their own in Clapham and pursue mountain climbing in the Alps.
[2] Their most famous expedition took place in 1869,[3] when they traversed the Seserjoch (Sesia Joch), a pass between Zermatt in Switzerland and Alagna in Italy that had only been ascended once before and never descended.
[1] Their traverse turned out to have been a mistake: they had intended to cross a more straightforward pass, the Lysjoch, but their guide, Jean Martin de Vissoie, had become lost and they descended to Alagna instead of Gressoney-La-Trinité as they had planned.
[2][4] Given the circumstances surrounding their traverse, their claim of success was met with scepticism, and the matter was not resolved until Giuseppe Farinetti of the Italian Alpine Club verified the Pigeons' account of the traverse and the British Alpine Club agreed that they had been successful.
[4] They remained active climbers through the 1880s, publishing a short account of their mountaineering experience titled Peaks and Passes in 1885.