Put the potatoes in a large saucepan, cover with cold water by about 1 inch and add 2 tablespoons salt. Bring to a boil, uncovered, over high heat, and then reduce the heat to medium-high and simmer briskly until fork tender, about 45 minutes. Drain the potatoes, reserving 1/4 cup of the water. Return the potatoes to the pan. Shake the pan over medium heat for about a minute to dry the potatoes. Remove from the heat.
Add the olive oil, lemon zest, lemon juice and the reserved cooking water to the potatoes. Mash the potatoes, skins and all, with a traditional potato masher to an even consistency. Fold in the herbs and season with salt. Serve hot with a drizzle of olive oil.