A large ice block on the route just above the Mount Everest base camp has forced hundreds of climbers and local guides to delay their attempt to scale the world’s highest peak. The serac between base camp and camp one was unstable and risky for climbers, said Himal Gautam of Nepal’s department of mountaineering on Friday. Officials were working with climbers and expedition organisers to assess the situation as climbers waited at base camp. According to the department, 410 foreign climbers had been issued permits to attempt to reach the Everest summit during the spring climbing season, which closes at the end of May. “Icefall doctors”, elite guides who lay the yearly climbing route by setting ropes and securing aluminium ladders over crevasses, usually finish the task by mid-April. The Sagarmatha pollution control committee, which deploys teams to lay the route, said it planned to assess the serac by aerial survey.…