Scotland Yard is looking into allegations of war crimes against Saudi Arabia, committed in Yemen.
The Metropolitan Police's war crimes team is carrying out a "scoping exercise" to understand whether or not a criminal prosecution could be brought.
The revelation comes in the same week the Prime Minister is due to pay the Saudi royal family a visit, and stress the need for "further intensification in relations" between the two countries.
A statement from the Metropolitan Police said: "On Thursday, 30 March 2017 the Metropolitan Police Service (MPS) received a referral of an allegation of war crimes, made against Saudi Arabia committed in Yemen.
"Following receipt of the referral, the MPS war crimes team (part of the Counter Terrorism Command) began a scoping exercise and contacted those making the allegations.
"There is no investigation at this time, and the scoping exercise continues."
Britain's potential role in the ongoing conflict in Yemen has been controversial, with the British government being urged to stop exporting arms to Saudi Arabia.
ITV News has seen evidence that British-made bombs and weapons are being used against civilians in Yemen, in what would constitute a war crime.
This is a charge that Saudi Arabia vehemently denies, saying the weapons seen by ITV News are older, and that the cluster bombs were in fact dropped in 2009.
The date the bombs were dropped is relevant, as in 2010 Britain signed the Cluster Munitions Convention which requires the UK to dispose all cluster munitions and prevent their use by anyone else.
Saudi Arabia has not signed the treaty, but if British cluster bombs are being used in Yemen, it could breach Britain's treaty obligations.
Last year, it was reported that then-Business Secretary Sajid Javid refused to stop exporting weapons to Saudi Arabia, even after being warned they could be used to kill civilians.