Two RAF jets have carried out their first combat mission over Iraq since Parliament authorised air strikes targeting Islamic State (IS) militants.
The Ministry of Defence said the two Tornado jets carried out armed reconnaissance operations but did not conduct any air strikes.
They gathered intelligence which would be "invaluable", the MoD added.
The mission comes after Parliament voted by 524 votes to 43 to take action against IS in Iraq, but not Syria.
The Tornado jets have now returned to RAF Akrotiri in Cyprus, seven hours after they took off.
In a statement, the MOD said: "Although on this occasion no targets were identified as requiring immediate air attack by our aircraft, the intelligence gathered by the Tornados' highly sophisticated surveillance equipment will be invaluable to the Iraqi authorities and their coalition partners."
It said that the "very presence of coalition airpower" would have a significant impact on IS.
"With no effective defence against air strikes, and knowing the precision with which coalition aircraft can hit them, the terrorists are forced to be much more cautious, keeping their forces dispersed and movement inhibited.
"They also know that should they concentrate to deliver an attack against Iraqi or Kurdish troops, aircraft are likely to arrive overhead very soon afterwards."
RAF Tornados have been flying reconnaissance missions over Iraq for the past six weeks, but these are the first flights since they have been authorised to launch air strikes.
The planes were loaded with laser-guided bombs and missiles.
The Tornados were supported by a Voyager air-to-air refuelling aircraft.
John Nichol, a former RAF navigator who was held captive in the Gulf War of 1991, said the difficulty with the mission was that IS does not have military infrastructure such as air fields or weapon dumps which can be destroyed.
"If there are no IS fighters on the ground and we're talking of a pick-up truck with some weaponry on the back - then there is nothing to attack.
"If IS know that the air assets are up there to hunt them down, they're not stupid, they're going to be hiding amongst the civilian population."
Analysis: BBC defence correspondent Jonathan Beale, at RAF Akrotiri, Cyprus
There were no guarantees that the two RAF Tornados that took off this morning would fire their weapons.
It was made clear that this would be a continuation of their reconnaissance mission, but with the key difference that they were now authorised to engage targets on the ground.
The fact that they returned fully loaded though is an indication that this fight will not be easy.
Britain is joining this fight more than a month after America launched its first airstrikes. IS will have had time to adapt on the ground.
It's also a reminder that the RAF is playing a modest role - US warplanes are carrying out dozens of sorties a day.
There will be more British combat missions as David Cameron has made clear that he's committed for the long term.
But while airstrikes have helped halt recent IS advances, they alone will not decide what happens on the ground.
IS - also known as Isis or Isil - controls large swathes of Syria and Iraq after rapid advances through the region in the summer.
It has been using the Syrian city of Raqqa as the capital of its self-declared caliphate.
The US has been carrying out air strikes in northern Iraq since mid-August, and was supported by the French since last week. About 40 countries in total, including several from the Middle East, have joined the US in taking action against IS.
Earlier, Prime Minister David Cameron said British aircraft were there to "play our part" in the international coalition amassed against IS which was being led by the "legitimate government of Iraq" and its security forces.
At least two British hostages are thought to be being held by IS - journalist John Cantlie and taxi driver Alan Henning, who had been delivering humanitarian aid to Syria.
- Formed out of al-Qaeda in Iraq (AQI) in 2013, IS first captured Raqqa in eastern Syria
- It captured broad swathes of Iraq in June, including Mosul, and declared a "caliphate" in areas it controls in Syria and Iraq
- Pursuing an extreme form of Sunni Islam, IS has persecuted non-Muslims such as Yazidis and Christians, as well as Shia Muslims, whom it regards as heretics
- Known for its brutal tactics, including beheadings of soldiers, Western journalists and aid workers
- The CIA says the group could have as many as 31,000 fighters in Iraq and Syria