London and Berlin - two great European cities with much to offer technology companies.
But now the German capital sees a chance to steal a march on its rival and perhaps take over as Europe's leading technology cluster.
Soon after the Brexit vote, letters began arriving from Germany at a number of small London technology companies.
One of them was addressed to Maz Nadjm, founder of SoAmpli - a social media advertising agency based just off the Silicon Roundabout on the fringes of the City.
The letter came from the office of Berlin's senator for technology and industry.