Dog is just 1 year old - golden retriever.
Recently he has started to go mad with sniffing on walks. Not just a bit of sniffing - he throws himself with wild abandon into bits of undergrowth every five paces. He'll be trotting along quite happily and then suddenly lurch forward to an interesting smell.
It is making walks extremely frustrating because he wants to roll around in nasty-looking patches of weed and delve in hedges and refuses to be distracted.
Any suggested strategies? He is entire, by the way.