A few days spent in Pu Luong Nature Reserve outside Hanoi recently were wonderful. An afternoon walk to Bat Cave ( a cave with loads of bats) was a special delight. Quaint ethnic Thai villages, friendly locals and magnificent scenery. But I now have an abiding worry about how places like this can be developed and not wrecked by tourism. The past decade has seen many places in Vietnam damaged by tourist development. Making sure locals are the real winners is the biggest challenge.