Brand new install of 5.7.10 on Mac OS X - ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

[Chris Jenkins]

I just downloaded and installed the Community edition of MySQL 5.7.10 on my Mac which is running OS X 10.11.2. As part of the install it displayed for me the default password for the user 'root'@'localhost' which I duly copied and pasted into a document for safekeeping.

However, when I try and connect to MySQL it always fails with:

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)

For example:

mysql -uroot -p
Enter password:

so I never the password that was apparently assigned at install time but I just get this error. I have tried the 'password 'reset' procedure but that has not resolved the issue.

What do I do now? MySQL appears to have failed at the first hurdle...