Britain joined the US-led bombing campaign over Syria on Thursday, hitting an oil field held by Islamic State jihadists just hours after a decisive parliamentary vote authorised air strikes.
Royal Air Force planes based in Cyprus carried out the "first offensive operation against Daesh terrorist targets inside Syria," the defence ministry said in a statement, using an alternative name for IS.
The strikes with Paveway guided bombs were carried out by four Tornado fighter jets and focused on targets in the Omar oil field in eastern Syria, 30 miles (48 kilometres) from the Iraq border.
The field "represents over 10 percent of their potential income from oil," the ministry statement said, adding: "Initial analysis of the operation indicates that the strikes were successful".
"We are going to need to be patient and persistent. This is going to take time," Cameron said.
"There will be strong support from our allies because they wanted us to join them in taking this action."
US President Barack Obama and French President Francois Hollande said they welcomed Britain's move.
Momentum to join the strikes grew after last month's terror attack on Paris in which 130 people were killed and Hollande on Thursday hailed a "new response to the call for European solidarity".
Russia is also conducting its own air strikes on Syria in alliance with Syrian forces and Kremlin spokesman Dmitry Peskov told Russian news agencies there should now be a single coalition to improve the "effectiveness" of the air campaign.
Prime Minister David Cameron's government was backed by 397 lawmakers with 223 opposing the bombing in a vote late on Wednesday after a sometimes raucous debate lasting more than 10 hours.
A wide range of MPs including main opposition Labour leader Jeremy Corbyn spoke out against air strikes, condemning Cameron's "ill thought-out rush to war" and saying his proposals "simply do not stack up".
But Labour's own chief foreign affairs spokesman Hilary Benn delivered an impassioned speech in favour of bombing, illustrating deep divisions in the party.
In the end, 66 of Labour's 231 MPs voted in favour, including 11 members of Corbyn's shadow cabinet.
Cameron also refused to apologise to opposition MPs for reportedly telling fellow Conservatives in a private meeting ahead of the vote they should not side with "a bunch of terrorist sympathisers".
- 'Important symbolically' -
Signup to our newsletter and follow us on Facebook and Twitter!
Britain already has eight Tornado fighter jets plus drones involved in the US-led coalition striking IS targets in Iraq, operating out of RAF Akrotiri in Cyprus.
They will be joined by six Typhoon jets, which took off from RAF Lossiemouth in Scotland, and two more Tornado fighters, which took off from RAF Marham in southeast England.
But experts question how much Britain, which has been wary of joining foreign conflicts in recent years after unpopular wars in Afghanistan and Iraq, would add to the campaign against IS in Syria.
"It will not make a big operational difference," said Professor Malcolm Chalmers of military think-tank the Royal United Services Institute (RUSI).
"It is important symbolically, useful operationally, but not transformative."
- 'Plotting to kill us' -
Cameron has pledged that Britain joining air strikes on Syria will be matched by a major diplomatic push to resolve the crisis.
The last Syria peace talks in Vienna held last month brought together 17 countries including Russia, the United States, Saudi Arabia and Iran.
The talks set a fixed calendar for a ceasefire followed by a transitional government in six months and elections one year later. Syrian opposition figures have called this unrealistic.
During the debate, the government also faced a string of questions about whether joining the international military action on Syria could make Britain more vulnerable to attacks from IS.
The last major attack on British soil was the July 7, 2005 bombings in which 52 people died.
And in June this year, 30 Britons were among 38 tourists killed in an attack at a holiday resort in Tunisia claimed by IS.
Officials say seven plots have been foiled by intelligence services in the last year alone.
Cameron said this figure showed it was right to take immediate action.
"These terrorists are plotting to kill us and radicalise our children right now," he said. "They attack us because of who we are, not because of what we do".