Conversation so far:
What are some of the songs Gary Barlow wrote?
In July 1996, Gary Barlow released his first single as a solo artist, entitled Forever Love and Sing is a song written by  Barlow and Andrew Lloyd Webber.
Does Gary Barlow have any collaborations?
In December 2011, Gary Barlow performed a duet with Michael Bublé singing Rule the World and Bublé's single, Home.
Did Gary Barlow write any number one hits?
Gary Barlow has written sixteen number one UK singles.
Did Gary Barlow have a publishing company?
In October 2007, Gary Barlow founded San Remo Live Publishings as an independently run management company to establish and support artists and songwriters.

Question: what is the most interesting thing in his songwriting career?
Self-contained rewrite: What is the most interesting thing in Gary Barlow's songwriting career?