From TFL:
From Saturday 21 May
Gower Street change to two-way traffic
From Saturday 21 May, Gower Street between Grafton Way and Euston Road will become two way to traffic. This means two-way traffic will run the length of Gower and Bloomsbury Streets between Euston Road and High Holborn completing this part of Camden’s West End Project.
As part of the changes, drivers will no longer be able to turn left onto Euston Road from Tottenham Court Road and should use Gower Street to access Euston Road westbound. You are advised to take extra time and care and follow the signage while all road users, including those walking and cycling, get used to the changes to the road layout.
Pedestrians are advised to take care when crossing Gower Street and Bloomsbury Street and remember to look both ways for traffic and cycles. The new pedestrian crossings are the safest way to cross the road and stewards will be on the street to remind people of the change for the first few days.
You can find more information on Camden’s West End Project West End Project – Transforming The Tottenham Court Road Area and current road updates Traffic status updates - Transport for London