Pour the pearl barley into a pan and sprinkle in a pinch of salt. Pour over 200ml boiling water and bring to the boil. Reduce to a simmer, cover with a lid and cook for 20 mins. When cooked, drain in a sieve or colander and rinse with cold water. Shake dry and tip into a bowl.
Trim the ends off the French beans. When the barley has 5 mins remaining, add the beans. Cover and continue to cook for the remaining 5 mins.
Trim the tops from the carrots and wash them. Roughly chop the carrot tops. Scrub the carrots and peel, and use the vegetable peeler to create ribbons. Trim and finely slice the spring onions.
Make the dressing by zesting the lemon into a bowl and squeezing in the juice. Whisk in 1 tbsp each honey, mustard and olive oil ,and a pinch of salt and pepper.
Add the carrots, tops, spring onions and watercress to the beans and barley. Spoon over the dressing and toss to combine. Pile onto a couple of plates and serve.