"This collective action sends a clear message that the worldwide community will not stand by and tolerate the use of chemical weapons", May said at a press conference, calling the military action "right and legal".
But shadow attorney general Baroness Chakrabarti questioned the Government's justification for the air strikes, telling BBC Radio 4's Today programme: "You can't use force under global law just to punish Syria for bad behaviour". We thank them both.
David Cameron, who was prime minister in 2013, tweeted on Saturday: "As we have seen in the past, inaction has its consequences".
She added that it would be a "crazy thing to do" to share information on targets with MPs.
In a related development, Middle East carrier Kuwait Airways said it would resume all flights to Beirut on Sunday after a three-day suspension due to warnings about flying close to Lebanese airspace.
She will say: "Let me be absolutely clear: we have acted because it is in our national interest to do so".
U.S. President Donald Trump said he was prepared to sustain the response until the government of Assad stopped its use of chemical weapons.
May added Britain and its allies had sought to use every diplomatic means to stop the use of chemical weapons, but had been repeatedly thwarted, citing a Russian veto of an independent investigation into the Douma attack at the U.N. Security Council this week. This massacre was a significant escalation in a pattern of chemical weapons use by that very bad regime. France, the USA and the United Kingdom have circulated a joint draft resolution on Syria at the UN Security Council that denounces the use of chemical weapons there and demands the establishment of an independent mechanism for investigating such incidents, AFP reported on Saturday evening.
But they backed action in Iraq the following year, and again in Syria in 2015, strictly limiting strikes to targets of the Islamic State group.
"And we can not wait to alleviate further humanitarian suffering caused by chemical weapons attacks".
In the video, released by the British Royal Air Force, ground troops can be seen preparing to deploy Panavia Tornado GR4 jets.