Thanks, Al R!
Although according to the latest edition of Which?, 'Anyone who is eligible for the state pension before April 2016 can benefit from an attractive annual rise of 10.4% for each year they defer it'.
Whereas if you qualify after April 2016, the annual increase will fall to a less attractive 5.8%.
Hence those currently aged 64 could still benefit from the better rate if they defer before reaching 65?