There are different theories.

The publisher would like us to believe that 'Matt Haig' is a human of 32 years of age living in the north of England.

This is unlikely. Far more probable is the rumour circulating among the Labrador community that Matt Haig is a Labrador, writing under a nom de plume, who is now housed in a special protective kennel provided by the publishers.

Another theory is that Matt Haig is a Springer spaniel, also writing under a pseudonym, who was deliberately attempting to expose the Labrador Pact to humans, and therefore rendering the Labrador’s secret powers of Paw Diplomacy and Wag Control all but useless.

Take your pick.