'Big Ben' can be seen in the centre of the belfry. Also note one of the smaller quarter bells in the upper foreground. Some idea of the size of the bells can be obtained by referring to the silhouette of a visitor in one of the arches, at the bottom right of the great bell. The strong platform beneath the bell was installed after the bell cracked to protect the lower part of the tower in case the bell fractured. Notice how the bell hammer moves within a large stirrup. The purpose of this is to prevent the hammer resting on the bell and damping its note before being withdrawn by the clock movement. (A rubber buffer at the base of the stirrup allows the hammer to deliver its strike to the bell when it descends at speed.)