Figures from the UN show that the UK expat population has been steadily growing over the past thirty years with 4.9m British citizens residing in other countries in 2017 - up from 3.8m in 1990.
Given this is such a sizable chunk of the population, it is surprisingly how scant the information we have on these citizens is.
There is no central register of expats kept by the UK government but it is possible to piece together a picture of the UK expat population by scrutinising the census data of destination countries.
The most popular destinations for expats
The United Nations produce a regular data set of global "migrant stock" that tracks the number of people of different nationalities living in different countries.
This data shows that the country containing the most UK citizens (apart, obviously from the UK) is Australia with 1.35m located there. This means Australia accounts for more than a quarter of Britain's expats.
Australia's popularity means that Oceania is actually the most popular continent for people to move to with all the expats in Europe coming in lower than Australia and New Zealand's combined total.
America is a distant second on the list of top individual countries with 748,206 expats while Canada is third and Spain fourth.
Chile's expat population has grown fastest for countries that had at least 1,000 UK citizens resident in 1990. Back then just 1,428 UK citizens lived there, but in 2017 this figure had risen to 18,901 - up by more than 1,200%.
The only continent where the UK's expat population has declined since 1990 is Africa, while numbers in Asia have more than doubled from 137,217 to 280,722.
What does the expat population look like?
Although we can tell how many UK expats there are across the world to some degree of certainty, there isn't much in the way of comprehensive coverage on what these populations look like demographically.
The Expat Insider Survey polls thousands of expats of all nationalities across the world each year. Although not as authoritative as census data we can use it to get a general sense of what British expats look like.
According to the 2018 edition of the survey the average UK expat is nearly 10 years older than that of the global average for expats, at 53 years old compared to 44.
They are mostly in relationships and 37 per cent of them have been living abroad for more than 10 years - much higher than the global average of 24 per cent.
A quarter of British expats are retired, which is more than double the global average of 11 per cent.
Their top three reasons for moving abroad are, in order of precedence, for a better quality of life; for love; and for a job.
Expats in the EU
The question of what will happen to British expats living in the EU has been a hot topic since the UK voted Leave in the 2016 EU referendum.
This has led the Office for National Statistics to produce a series of reports looking at migrant populations in selected specific countries across the EU. They give much more robust pictures of UK expat populations in the areas that they cover.
In Spain, for instance, the proportion of expats who are of retirement age has more than doubled since 2006, with higher concentrations of expats located on the southern coastal areas such as Malaga.
Indeed, the number of people collecting UK pensions from abroad has risen fairly significantly in Germany, France and Ireland as well as Spain.
While a large number of British expats have retired, it seems the majority are actually still economically active. In France, for example, 52 per cent of expats were in employment, while in Germany the figure was as high as 79 per cent.