The claim: The UK exports five times as much to the EU as it does to the Commonwealth.
Reality Check verdict: Yes we do. The UK's exports of goods and services to the Commonwealth in 2014 were worth £47.8bn. The comparable figure for the EU was £228.9bn. It's worth noting that the UK does plenty of business with countries that are part of neither group - for example, we sell twice as much to the USA as we do to our biggest EU partner, Germany.
Is he right?
Figures from the Office for National Statistics show our exports of goods and services to the Commonwealth in 2014 were worth £47.8bn.
The comparable figure for the EU that year was £228.9bn, which is slightly less than five times the Commonwealth figure.
So the figure the former prime minister used is accurate. But why did he choose this one? We have historical links with the Commonwealth, but our biggest customer in the Commonwealth is only our thirteenth biggest in the world.
There are 52 other countries in the Commonwealth. We know from the ONS Pink Book (table 9.3) which are our biggest customers in the Commonwealth. The top five are India, Australia, Canada, Singapore and South Africa.
But some of the Commonwealth countries are very small, including Nauru and Tuvalu, both of which have populations of about 10,000.
What other figures could he have used? In 2014 we exported £88bn of goods and services to our biggest single customer, the USA, which was twice as much as our second biggest customer, Germany.
We sell more than half of our exports to seven countries, four of which are EU members.
Source: ONS Pink Book. Note: The figure for the Netherlands may be enlarged by the so-called Rotterdam Effect, in which goods being shipped from its ports are counted as exports to the Netherlands.
Read more: The facts behind claims in the EU debate
On Friday's Today Programme, former Prime Minister Sir John Major said that the UK exports five times as much to the European Union as it does to the 52 countries of the Commonwealth.