 In 1345 , while Grosmont was in France , his father died . The younger Henry was now Earl of Lancaster – the wealthiest and most powerful peer of the realm . After participating in the Siege of Calais in <unk> , the king honoured Lancaster by including him as a founding knight of the Order of the Garter in <unk> . A few years later , in 1351 , Edward bestowed an even greater honour on Lancaster when he created him Duke of Lancaster . The title of duke was of relatively new origin in England ; only one other <unk> title existed previously . 
