Holland was particularly involved in the attack on the French fleet at Mers-el-Kébir in July 1940.
A British fleet, Force H, was despatched under Admiral Sir James Somerville to insist the French either demilitarize their ships or hand them over to the British, to prevent their capture by the Germans.
Holland, as a French speaker with experience from his time as naval attaché in Paris, was sent to deliver the terms and enter negotiations with the French naval officers.
He was taken into Mers-el-Kébir with the ultimatum aboard HMS Foxhound early on 2 July.
Holland and Somerville were strongly opposed to the use of force, hoping that a show of strength would be enough to convince the French to avoid fighting.

Apparently offended by Somerville's sending a junior officer to deal with him, the French commander, Admiral Marcel-Bruno Gensoul at first refused to meet Holland, and delegated his flag lieutenant, Bernard Dufay, to meet him instead.
The negotiations dragged on for several hours, with the French unwilling to agree to terms.
With French reinforcements reportedly en route, Holland tried to convince Somerville that the French crews were being reduced, and would sail to Martinique.
But it was too little and came too late, the Admiralty pressed for a resolution and Holland was ordered to break off negotiations, and was taken back to his ship by HMS Forester.
Twenty minutes after his arrival the British attacked, sinking several ships and badly damaging others.
Holland was particularly involved in the attack on the French fleet at Mers-el-Kébir in July 1940. A British fleet, Force H, was despatched under Admiral Sir James Somerville to insist the French either demilitarize their ships or hand them over to the British, to prevent their capture by the Germans. Holland, as a French speaker with experience from his time as naval attaché in Paris, was sent to deliver the terms and enter negotiations with the French naval officers. He was taken into Mers-el-Kébir with the ultimatum aboard HMS Foxhound early on 2 July. Holland and Somerville were strongly opposed to the use of force, hoping that a show of strength would be enough to convince the French to avoid fighting.
Apparently offended by Somerville's sending a junior officer to deal with him, the French commander, Admiral Marcel-Bruno Gensoul at first refused to meet Holland, and delegated his flag lieutenant, Bernard Dufay, to meet him instead. The negotiations dragged on for several hours, with the French unwilling to agree to terms. With French reinforcements reportedly en route, Holland tried to convince Somerville that the French crews were being reduced, and would sail to Martinique. But it was too little and came too late, the Admiralty pressed for a resolution and Holland was ordered to break off negotiations, and was taken back to his ship by HMS Forester. Twenty minutes after his arrival the British attacked, sinking several ships and badly damaging others.
Cedric Holland