Consequent upon this alteration in the economic conditions of the nation, the need for the impregnable stronghold of the past ages ceased to exist, and in many parts of England, but more especially in the south and east, the existing structures were largely altered or added to in order to afford conditions suitable to the changed amenities of social life. These alterations in nearly every case were made at the sacrifice of efficiency, and many castles which had played a notable part in the history of the nation became merely the residences of their lords, who made no attempt to put them to their original uses in time of war. Arundel, the great midland castles of Warwick, Kenilworth, and many others, fall under this category. So far as gunpowder is concerned the part which it played in causing the abandonment of the feudal castle is strangely varied and dependent upon local circumstances. A well-found castle with an efficient and adequate garrison, supported by an army in active operation in the field, had no more to fear from an attack in the fifteenth century than it had in the thirteenth, perhaps not so much. Very few bombards of the period mentioned could throw stone shot weighing over 150 lbs., whereas the medieval trebuchet could hurl a missile of twice that weight, or even more, and to almost as great a distance. The effect of low-trajectory cannon upon castle walls in the fifteenth century under ordinary conditions may almost be left out of consideration, so small was the calibre. It is true that Sir Ralph Grey, when besieged in Bamborough Castle in 1464, was forced to surrender in a short space of time by the army of the Kingmaker, who used his basilisks, aspiks, serpentines, dragons, syrens, and sakers with excellent effect; but we may justly claim that this was an exception, the configuration of the ground enabling Warwick to place his pieces close up to the walls, while Grey could look for no effective relief from a sympathetic army outside. Ten years afterwards the Castle of Harlech, under the able governance of Davydd ap Ifan, held out against all the force that Edward IV. could bring to bear upon it, and was the last of the castles garrisoned by Lancastrians to render up its keys.