1. Tear the bread into small pieces and place in a large bowl. Cover with ice-cold water (at least 750ml) and set aside for 10 minutes. In a powerful blender, whizz the tomatoes, olive oil, sherry vinegar and garlic until smooth.
2. Squeeze the excess water from the bread and add the bread to the blender (reserving the water). Blend until smooth and, with the motor still running, loosen with about 400-500ml of the ice-cold water, until you have a thick, yet pourable soup. Chill until ready to serve.
3. Divide between 4 bowls (or 8 glasses, if serving as a starter). Top with the ham and egg then finish with a drizzle of oil, a good grinding of black pepper and sprinkle with a handful of Greek basil leaves.