July 3, 1940 Execution of Catapult
In England before dawn naval patrols boarded the French Ships and overpowered the sailors on watch and sent the crews ashore. only one incident of violence occured, this was on the French submarine Surcouf where one French Sailor was killed and 1 British sailor was killed and 3 wounded.

(I have also read that it was 2 British Officers and 1 French seaman killed and a British petty Officer wounded) Gary

This is an excert from HMS Revenge notice board.

HMS Revenge notice board

After the French had surrendered, the French fleet had to be prevented from falling into German hands. I forget whether we were in Pompey or Devonport, but the old battleship Paris was tied up astern of Revenge and the submarine Surcouf was tied up alongside her. In the early hours of one morning we went to action stations and sent boarding parties to take both ships. The sentries on the Paris were taken by surprise. The first man down the ladder on the Surcouf was leading seaman Webb. He was shot and killed by a French officer. The British officer following Webb then killed the Frenchman

However smooth the operation in England went was no precurser of what was to happen in North Africa.  At Mers-el-Kebir Force "H" Including the Battleship Hood, and Carrier Ark Royal. blockaded the harbor and delivered an ultimatom outlineing the above mentioned options. French Admiral Gensoul in a buy for time to get his ships in shape for a fight, kept up a dialog with the British officer sent to negotiate.  Shortly after 1pm Swordfish from the Ark Royal mined the harbor entrance, This enraged the Gensoul and made him belive the British were negotiating in bad faith. at 4:46pm with negotiation still in progress the Admiralty radioed Sommerville to "Settle matters quickly or you will have reinforcements to deal with".  At 5:15  Sommerville signaled the Dunkerque "If none of the proposals are acceptable by 5:30 It will be neccesary to sink your ships. The negotiation team headed by Captain Holland had failed and as he stepped onto the gangway he heard "Action stations" Blair across the French fleet. Holland then raced for the harbor entrance.  The Hood opened fire with her 15in Guns shells began smashing into the French Bretange. The Port nearly disappeared in a caldron of flame and greasy smoke. The French  fleet returned fire, but ineffectivly. In less than a quarter of an hour the harbor had become a smoldering tangle of blackened steel. Gensoul signaled for a cease-fire, then Somerville messaged "Unless I see your ships sinking I shall open fire again". To save any accidental loss of life Somerville took force H out of range, Confident in his mines. But the French Battlecruiserm Strasbourg made a daring escape, picking its way through the wrecks and minefield. The Strasbourg was nearly free when a Swordfish from the Ark Royal spotted her, promptly 6 more swordfish were sent in pursuit. And even the Hood turned to chase briefly, but rather than leave the harbor unguarded again Sumerville broke off.
Despite the Starsbourgs escape the Dunkerque,Bretagne,Providence and Mogador were beyond escape and lay crippled or sinking. more than 1,200 men who had been fighting beside the British had died under the guns of their former allies. For the British effort they lost not a man.
In Alexandria Cunningham had been ordered to present virtualy the same ultimatum to his friend Admiral Godfroy and sent an formal invitationto meet on board the Warspite at 7a.m. As Cunningham read off his ultimatum Godfroy strained to keep in control of his features. Gofroy asked for time to study the proposals, and the men agreed to decide by 11:30. At noon Godfroys response came, He had decided that he could neither join the British or disarm his ships without authorization of the Vichy government. He therefor would take his ships to sea and scuttle them however this would take 48hrs to complete. Admiral Cunningham agreed to this, but since London was skeptical of the plan, the Admiral personaly sent a message asking for Godfroy to make some sogn to prove to the British government that he did not intend to escape. Godfroy agreed almost at once, and began draining fuel oil from his bunkers. Cunningham relaxed thinking the crisis adverted.
At 8:15 came a message from London: "Admiralty note that the fuel oil is being discharged by French ships. Reduction of crews, especialy ratings,should however begin at once by landing or transfer to merchant ships. Before Dark tonight do not RPT Do not fail". this was tantamont to taking over the ships, Cunningham Ignored this order.   Then Godfroy learned the ultimatum at Mers-el-Kebir, and had been ordered to take his fleet to sea by the French Admiralty. He would attempt to confirm this order but in the meantime would halt the offloading of fuel. Godfroy told Cunningham that these orders had removed the option of scuttleing his fleet. However he had made a promise and would keep it. If directly ordered to do so by the Royal Navy, He would scuttle the squadron under Cunningham's guns. He added in a nice gallic way he would scuttle them to block the harbor as little as possible. Cunningham before retiring around midnight cabled london about the new sitiuation and that he planned to order the French fleets scuttleing in the morning.  Cunningham was awoken before 7am with a urgent message: An angry message from Godfroy who had learned of the action at Mers-el-Kebir. and due to this engagement repudiated all promises, claiming the British had made them to an officer who was dealing in bad faith. Godfroy intended to head for sea,fighting his way out if neccesary. Across the harbor French ships were raising steam and preparing for action. Cunningham wrote later "the Crisis had come there seemed to be no chance of evadbg what I wished to avoid at all costs, a battle in Alexandria harbor. Orders went cracking throught the British fleet. Battleships manuvered to bring their guns to bear on the French, Tampions came out of the muzzles and the guns were trained. Destroyers and subs were ordered out of the harbor to intercept any escaping vessel.  Cunningham called his staff and laid out his plan. Clearly Godfroy had to fight to preserve honor, and he needed an excuse not to fight. The British would go over Godfroys head to his officers, hopefully spurring them to peacefull rebellion. Immediatly a message was flashed to all the French ships in the open. explaining the helplessness of the French and the British's desire not to kill the French. And assured them that the terms offered by the British would not cause a loss of honor. Also all French ships had British Laisons who went and talked with the ships commanders.
Godfroy then summoned his commanders to the Duquesne where they deliberated for over an hour. Then the British received an signal, Godfroy requested to come over aboard the Warspite. Upon ariving he said with great dignity he was yeilding to overwhelming force.
Over the next few days several skirmishs occured between the French and British, At Dakar the  French Battleships Richelieu was torpedoed, and Gibralter bombed by the French. These actions left a decidedly anti British sentiment in French North Africa.