From Guildford the down-line followed the Wey valley to Godalming, then, over Milford and Witley, proceeded to Haslemere and on through Petersfield towards Portsmouth. Roughly parallel to it, the upline passed over Worplesden, Tongham, Puttenham, Elstead and Grayshott. Between the Hog's Back and Hindhead there were points where the two lines were not more than six or seven kilometres apart. The distance was too small for careless flyers-particularly at night and when they had taken half a gramme too much. There had been accidents. Serious ones. It had been decided to deflect the upline a few kilometres to the west. Between Grayshott and Tongham four abandoned air-lighthouses marked the course of the old Portsmouth-to-London road. The skies above them were silent and deserted. It was over Selborne, Bordon and Farnham that the helicopters now ceaselessly hummed and roared.