If you've got an Android phone download the free app 'UK Motorcycle Parking'. Shows you where all the bays are, and whether they are free or paid. City of London is free, but Westminster is £1 per day and you can pay by phone. As a result all of the COfL bays on the border are chock full but the Westminster ones usually have spaces. Leicester Square is very much Westminster. Some Bikers will daisy chain their locks to improve security