Only the whistles on the 1st and 2nd funnles worked. The other two were just for show. This is related in the Shipbuilder Midsummer 1911 special edition:
"The whistles are the largest ever made. Each set consists of three bell domes grouped together with a suitable branch plate, as shown in Fig. 71. The three domes are 9in., 15in., and 12in. diameter. The total height from the base of the branch piece to the top of the centre dome is 4ft. 2 1/2in, and the extreme width over the outer dome is 3ft. 6in. the total weight of the three domes and branch pieces is about 6 3/4cwt. One set has been fitted on each of the two foremost funnels. The whistles are electrically operated, the officer on the bridge having merely to close a switch to give the blast, and there is also an electric time-control arrangement, fitted on the Willett-Bruce system, whereby the whistles are automatically blown for 8 to 10 seconds every minute during thick weather."