Phillip Hammond's promotion to foreign secretary was hit by twin crises last night, as the world reacted with shock to the shooting down of flight MH17 and Israel's ground invasion of Gaza.
The immediate preoccupation was with the Malasian Airlines flight from Amsterdam to Kuala Lumpur, which was shot down last night killing all 283 passengers and 15 crew members on board.
Hammond would not be drawn on exactly how many Brits were onboard, but it is thought there were somewhere between six and nine, alongside 154 Dutch, 45 Malaysians, 27 Australians, 12 Indonesians, four Germans, four Belgians, three Filipinos and one Canadian.
At the UK's request, the United Nations security council is meeting tomorrow afternoon to discuss the crisis.
"We're determined to get to the bottom of understanding what has happened here," Hammond said.
"As yet, we do not have any definitive information about how this incident occurred and I don’t want to speculate at this stage.
"We believe that there must be a UN-led international investigation of the facts. We are prepared to make Air Accident Investigation Branch assets and specialists available to aid such an investigation.
"We do believe that there were British nationals on board the flight. We are working through passenger data, cross-checking it and referencing it to establish exactly the numbers and identities of those British nationals, and as soon as we have further information we will be in contact with the families."
Hammond said the UN civil aviation organisation was ideally placed to lead the international investigation.
There are growing calls for parliament's recess – due to start next Tuesday – to be delayed so MPs have time to debate what had happened.
"If Russia/Russian missiles have shot down passenger plane as being suggested Europe enters a new unchartered [sic] era. Parl recess on hold," Labour MP John Mann said.
The prime minister chaired an emergency on the crash this morning.
"If, as seems possible, this was brought down then those responsible must be brought to account and we must lose no time in doing that," he said afterwards.
"It is an absolutely shocking incident and cannot be allowed to stand."
It is far from clear who is responsible for the disaster, with claim and counter-claim starting to dominate the debate.
Yesterday, Russian president Vladimir Putin blamed the Ukrainian government.
"This would not have happened if there were peace on this land and, certainly, the state over whose territory this occurred bears responsibility," he said.
Russian sources said they had intercepted phone calls showing Ukrainian government forces were involved.
They also claim Russian loyalist groups, who have been blamed by Ukraine for the attack, do not have access to the Buk ground-to-air missile which took down the Boing 777.
Officials in Kiev deny any involvement, with President Petro Poroshenko calling it an "act of terrorism".
Meanwhile, Hammond was dealing with a separate crisis in the Middle East, after Israeli forces entered Gaza.
Hammond adopted the same stance of his predecessor and urged Israel to "act proportionately".
Labour used to be overwhelmingly supportive of Israeli military actions in a manner which was comparable to the near-unanimous support for the country in Washington.
But the UK's rhetoric under the coalition became chillier, with Hague issuing more critical statements about Israel's actions.
Hammond called on the Hamas rockets to stop but also insisted Israel needed to tread carefully in its response.
"We have been calling on Hamas to end the rocket attacks on Israel for days now. Israel has a right to defend itself, but in doing so it has to act proportionately and it needs to take all steps to minimise civilian casualties," Hammond said.
Palestinian officials said eleven had bene killed already following the ground invasion, but Israel claimed it had killed 14 militants.
Sources on the ground are critical of Israel's assessment of militants. It is thought that three quarters of the people who have died since the fighting began some days ago have been civilian.
One Israeli soldier was killed and two injured.
Israel plans to target rocket launchers and tunnels to stop Hamas firing rockets into its territory.