THE upcoming royal birth is set to spark a £100 million retail bonanza – with the Queen even cashing in.Her Majesty’s palace shops will sell baby clothes and souvenirs celebrating the latest arrival in the Windsor family.All profits will go to the Royal Collection Trust which is used for the upkeep of palaces and art.Prince Charles is also set to profit with handmade baby shoes going on sale in his Highgrove shop.They will either be emblazoned with a Union Jack design or tractors on the front – priced at £22.50 a pair.Professor Joshua Bamfield of the Centre for Retail Research, which is analysing the economic impact of the royal birth, said: "The retail sales effect of the royal baby could end up being much more than £100m.”