At age of 30 Isabella was still unmarried when the Burgundian house of Valois provided her with an offer of marriage in 1428.
On 19 October 1428, Philip sent a delegation from Sluys led by his chief counsellor, the Seigneur de Roubaix, that arrived in Lisbon on 16 December after calling at Sandwich until 2 December and acquiring two more ships.