Wash the watercress and leave to soak in a large bowl of cold water.

Whisk the vinegar with the sugar and a pinch of salt. Toss the radish in the vinegar and leave to pickle.

Heat the oven to 200C/180C fan/gas 6. Put the shallots in a roasting tray and coat in the olive oil. Season. Arrange the shallots cut-side down and roast for 45 mins.

Meanwhile, put the potatoes and mint in a pan. Cover with cold water, bring to the boil and cook for 10 mins until tender. Leave to cool in the water, then drain, cutting any bigger potatoes in half.

Peel off the roasted shallot skins and discard. Pull apart the shallot halves and toss in a salad bowl with the potatoes, dressing and the roasting oil. Drain the watercress, then add that, season, and scatter over the pickled radishes and a little cider vinegar. Toss everything together and serve.