"I did not press for London to be the meeting-place; personally
I was inclined to Paris. The French would be pleased by
the choice of Paris, and the Conference would start with
that asset of good-will."
Foreign Secretary Edward Grey, Twenty-Five Years, at 255.
"The conference we proposed, or The Hague reference proposed by the Czar,
would have settled the quarrel in a little time. I think a conference
would have settled it in a week..."
British Foreign Secretary Edward Grey
"The important thing was to gain time by mediation in Vienna."
The Austrian archduke, the heir apparent, was assassinated in Sarajevo on Sunday, June 28, 1914. Vienna, upon receiving word of the regicide by telegram about 11:30am that day, was outraged. The British Foreign Office received news of the regicide by telegram at 16:00 and again by telegram at 18:00 that day.
If the British Foreign Secretary Edward Grey had been a bit more broad-minded about Europe - as HM Queen Victoria certainly was - he might have considered an informal meeting of the Great Powers' representatives. In 1914, the French Riviera was a spectacular destination, popular with French, German and Russian leaders, including British King Edward VII and his mother, the famous HM Queen Victoria.
London to the French Riviera in under 28 hours. The British Foreign Secretary might have invited the foreign ministers of France, Germany, Austria-Hungary and Russia to meet/vacation at the French Riviera.
Relax a couple days, enjoy the georgeous Mediterranean views, the beach/swimming, the best French cuisine, spirits, music, perhaps some female friends, then informally have the representatives of the Great Powers ajourn to discuss the local but still-dangerous Austria-Serbia political crisis.
Wagons-Lits Orient Express 1890
In June-July 1914, representatives of the Great Powers of France, Germany, Britain, Austria-Hungary and Russia could have stepped onto Wagon-Lits railway and been whisked in as little as 20-48 hours to the fabulous and luxurious French Riviera for an informal Great Powers meeting.
It is not easy to pinpoint a more luxurious and relaxed location for resolving intense local political crises in Europe. That is, IF the British Foreign Secretary Grey had been willing to cross the Channel, something the European travelers British Queen Victoria and British King Edward VII did all the time.