Reality Check: Can we believe petition signature numbers?
The numbers of people who have signed a petition calling for President Trump not to be allowed to make a state visit to the UK has been widely reported.
Can it be believed?
The number reported by Parliament's petitions website is at about 1.8 million.
There is also a petition saying that President Trump should be welcomed with a state visit, which has passed 200,000 signatures.
Any British citizen or UK resident is entitled to sign a petition on the site and asked to confirm their status when they do so.
An email is then sent to the address given, containing a link that signatories must click on before they are counted.
The House of Commons says: "All petitions are checked for fraudulent activity, using both automated and manual checks. The checks prevent fraudulent signatures being added to petitions by individuals trying to repeatedly sign, or automated attacks (bots)."
It adds that there is a balance to be made between making it easy for people to sign while making it harder to do so repeatedly.
The procedures have been tightened up since last June, when at least 77,000 fraudulent signatures were removed from a petition calling for a second EU referendum.
An investigation was launched after posts were found on websites from people claiming to have written programs that would automatically sign the petition thousands of times.
The House of Commons will not give details of either the original or new security procedures it has put in place.
It is not immediately obvious how the system works to prevent people voting more than once, but fraudulent signatures have been disqualified in the past.
It should be said that both petitions have received considerably more than the 100,000 signatures, above which petitions "almost always" trigger a debate in Parliament.