cazatou: When the crew selected the waypoint change they would have been approx 600 metres from the cliffs
Not according to Boeing: 8-7D20-DSS-0306, Enclosure 4 Dated: June 18, 2002 (On MoD website).
Page 12 has a chart
Figure 6. Vertical flight Path to Last Altitude Update showing terrain and distance based on a closing speed of 158.5 knots. That shows waypoint change at ~ 1,900ft or 600m from landfall at
sea level. Based on the possible cruising altitude variations discussed then waypoint change was estimated at between 5,000 and 5,300ft from the 'cliffs' ie 1,500-1,600m.
EG