Just to advise that I had my bag snatched by someone on the back of a motorbike, after just arriving in Medan. Fortunately, the strap broke and I was not dragged along the road. Unfortunately, my passport was inside. It is a horrible city and the pavements are full of parked bikes, food stalls etc and so often you are forced to walk in the road. The police did not care much and said that it was probably drug addicts, as the city is full of them, it happens all the time, and then just laughed about the Bali 9, who had been executed the day before. I had to fly to Bali (better than Jakarta!) as there is not a British Embassy in Sumatra. The Embassy have not been overly helpful either and just keep saying things like "maybe/perhaps/possibly" when I need definite answers as I had planned on traveling to other SE Asian countries.
AVOID IF YOU CAN AND BE VERY CAREFUL AS IT APPEARS IT HAPPENS ALL THE TIME.