Waymo is stepping up preparations for its UK rollout after its driverless vehicles were spotted on the streets of London, as the Alphabet-owned firm faces safety scrutiny in the US. The self-driving vehicle firm has confirmed it is testing its robotaxis in the capital ahead of a planned passenger launch this year, marking its second international market after Japan. This move comes as Waymo expands its paid, fully driverless ride-hailing service in the US, most recently launching in Miami. The Miami rollout makes Waymo the first operator to run…