The £2.5bn project was given the green light by Ofgem (the Office of Gas and Electricity Markets) in 2024.
Onshore work is already underway and offshore construction is expected to begin in the summer.
At the cable's two junction points, Torness in East Lothian and Hawthorn Pit in County Durham, two converter stations will be built, one at each end of the cable, to convert the electricity from alternating current to direct current, the most efficient form for it to travel over long distances.
Specialist ships will then be used to install the cable on the seabed and bury it along the route before connecting it to the grid.
Today in Torness, SP Energy Networks CEO Nicola Connelly and National Grid Electricity Transmission Chairman of Strategic Infrastructure Carl Trowell met with East Lothian Housing Minister Paul McLennan to mark the start of construction.