In 1864, the Italian revolutionary Giuseppe Garibaldi visited London. The visit was one of the great events of the age. Vast crowds welcomed him wherever he went and lionised him.

But Britain was finding it had limited leverage over continental issues. It was also finding that the Mediterranean offered a better prospect for effective British intervention because there the Royal Navy was in its element.

There was also a new threat, or rather a perceived new threat: one of the British commissions asserted after a visit to Malta that "the introduction of steam ... is calculated to strike a vital blow to the naval supremacy of the British Empire".

But the construction of an ironclad, propeller-driven, all-steam fleet in the Mediterranean in the 1860s confirmed that steam had in fact clinched, not undermined, Britain's Mediterranean power.

It was one thing for the British government to face crises at either end of the Mediterranean in, say, Greece or Spain and their immediate environs. But when trouble spread to the central Mediterranean - the middle parts of the Middle Sea - the issues became very serious.

This above all meant Italy, where Napoleon had caused so much havoc. In Sicily, the increasingly beleaguered insurgents sought to activate C-in-C Mediterranean Fleet Admiral Sir William Parker's help by signalling their loyalty to the British connection. But the Admiral stood by, and continued to do so when King Ferdinand, freed from fear of disorder in Naples itself, dispatched an expedition of 20,000 troops to the island in September 1848.

A ferocious bombardment began on Messina (earning the King his lasting pejorative nickname in Europe of "Bomba").

HMS Gladiator took off 1,500 frightened women and children from the shore. An uneasy calm held into the new year, but in March 1849 Ferdinand ordered a fresh offensive. Catania was razed and Neapolitan forces advanced towards Palermo, leaving burning villages in their wake. To save the capital from the fate of other towns, the rebels finally capitulated, at which point Parker allowed some of their leaders to avoid execution by scrambling aboard the British warships.

In a tense parliamentary debate, Palmerston defended his actions - and those of Parker - as a defence of the rights of British nationals in foreign lands. At the climax of his address on 9 July 1850 he famously stated it to be a fundamental principle of British foreign policy that, just as "the Roman ... in days of old held himself free from indignity when he could say 'Civis Romanus sum', so also a British subject, in whatever land he may be, should feel confident that the watchful eye and strong arm of England will protect him against injustice and wrong".

Subsequently, the Mediterranean Fleet wintered quietly in Malta. The island could not be wholly unaffected by the recent turbulence. During the 1840s it had become a haven for displaced radicals from Italian states. An edgy and secular Italianism in some classes interacted with growing irritation about the continuing stream of British military governors.

The appointment of a civilian and Catholic official, Sir Richard More O'Ferrall, as Governor in October 1847, was an attempt to damp down such grievances.

O'Ferrall put more locals into senior government jobs, so that by the end of the 1840s five of the eight most important departments had Maltese heads. He also inaugurated administrative reforms and undertook public works to boost employment, including a new commercial port and more bonded warehouses.

With advanced constitutions springing up throughout Europe, some sort of elected element in Malta's government could not be put off any longer. Such a system was approved in May 1849, with lively elections taking place the following August, though the electorate remained very small (3,767 voters in Malta and Gozo combined).

But O'Ferrall's attempts were compromised by the arrival of more Italian refugees fleeing from resurgent absolutism. Some 800 came to Valletta on Parker's ships from Sicily, and on vessels from Rome's Civitavecchia. These people were destitute and anticlerical, and on both counts O'Ferrall would have barred them if he could; Malta was, in his view, in no position to be generous.

The Governor drew the line when a French steamer tried to dock with 200 more "paupers and democrats". Their exclusion reduced the French captain to apoplexy, and even the Foreign Office in London regretted that "the common law of hospitality" was denied.

Maltese radicals, already critical of the Governor's habit of riding roughshod over elected members with the help of the official majority in the Council, were handed a weapon with which to beat him and they made full use of it. Escalating bitterness led to the Governor's resignation in frustration in 1851.

The experience of both Seaton in the Ionian Islands and O'Ferrall in Malta exhibited a paradox that was often to be played out in the British Mediterranean. What seemed to London and its agents to be conciliatory and liberal concessions, far from being enthusiastically and gratefully embraced, frequently met with a hail of brickbats from local opponents.

Malta and the Ionian Islands, however, differed in one key respect. The significance of the former in British naval strategy was on the rise, while that of the latter was on the same.

During the 1820s and 1830s more money was spent on the fortifications of Corfu - and at times more military engineers kept there - than on either Malta or Gibraltar. But during the 1840s this began to change. The growing British stake in the eastern Mediterranean meant that the centrality of Malta gained an extra premium as a place for the preparation and launch of expeditions, underpinned by the British possessing no lodgement in or adjacent to the Levant.

This process received a boost in the period leading up to Anglo-French hostilities against Russia. Ostensibly the Crimean War had Mediterranean roots in arguments about religious rights in Jerusalem's Holy Places, but the disputes were organically connected to diplomatic rivalries.

On 23 March 1853, Lord Clarendon, Foreign Secretary in a ministry led for the first time by Palmerston as Prime Minister) suddenly terminated talks with Tsar Nicholas in which a likely carve-up of Turkey had been contemplated. The Mediterranean navies of Britain and France were ordered on 7 June to head for the Dardanelles. Parker's successor as Commander-in-Chief, Sir William Dundas, issued his instructions that evening and the leading vessel, HMS Arethusa, eased out of the Grand Harbour of Malta and turned to the east. The Crimean War was about to begin.

Extra troops and shipping poured into Malta. On 30 November a Russian squadron made a dash across the Black Sea and annihilated the Turkish fleet at Sinope, the last naval battle fought completely under sail in the Mediterranean region. What the Russian action did was to frame and legitimise a war fought to keep the Russians as far away as possible from the Mediterranean.

The British expedition (already ravaged by the plague) was despatched post-haste towards the Crimean peninsula in the company of their French allies. The attack by six British and six French warships on the naval installations at Odessa on 22 June began the Crimean War proper.

The British objective in these operations was the destruction of the Russian fleet and arsenal at Sevastopol. But the Russians blocked the approaches to Sevastopol by sinking seven of their own warships in the harbour. To counter this, Sir Edmund Lyons, deputy to Commander-in-Chief Dundas, successfully pressed for the full-scale assault on the type of Algiers and Acre. But the assault on 17 October 1854 was a fiasco in which more than 300 British sailors died.

Plague more than anything else finally choked off the war. Sevastopol eventually fell on 11 September 1855, though most Russian troops had left beforehand. Admiral Lyons wanted to go on and devastate Odessa, with all its commercial wealth but the British public and politicians lost interest and patience. The expeditionary force endured one more cold and famished winter.

After the Crimea there was a "back to basics" in British strategy and this meant a concentration in the Mediterranean proper on established positions. Heavy British guns evacuated from the Crimea and some captured artillery was dropped off at Malta and Gibraltar instead of being taken back to England.

Malta in particular had received a boost. It had been the de facto rear base for the expedition to the Crimea. In spring 1854 there had been three regiments of Guards, the Rifle Brigade, four infantry line regiments, substantial numbers of Zouaves from Algeria, plus the combined Anglo-French naval presence crammed into the harbour and island.

If the war was bad for many, it was excellent for most Maltese. The activity triggered a boom to compare with that following Napoleon's continental blockade of British trade after 1806. When troopships left for the eastern battlefront, excited crowds lined the harbour. The "time of Crimea" passed into Maltese folklore as a time of plenty. Not surprisingly, political discontents ebbed away.