Bring a medium-sized saucepan of water to the boil before carefully lowering in the egg. Boil for 8 minutes, then drop in the green beans and simmer for a further minute. 

Meanwhile, heat the coconut oil in a frying pan over a medium to high heat. Carefully lay in the tuna and fry for 1 minute on each side. This will give you rare tuna – if you like it more cooked, fry it for a further minute on each side. Remove the tuna from the pan, season and leave to rest while you put the rest of the salad together. 

Drain the egg and beans in a sieve or colander, then run under cold water until cool enough to handle. Peel the egg and slice in half. Put the beans, lentils, spinach, sundried tomatoes, walnuts, olive oil and vinegar into a bowl, along with a generous pinch of salt and pepper. Gently toss all the ingredients together, then transfer to a plate. 

Top the salad with the tuna, sliced if you like, and the egg.