He was marrying the ravishingly pretty Princess Alexandra, whose father would soon become King Christian IX of Denmark and whose brother was about to be named King George I of Greece.
The Princess Diana of her day, Alexandra was already wildly popular with the British public and it was a dazzling ceremonial occasion.
The event also marked the first public appearance in Britain of the Queen's eldest grandson, four-year old Prince Wilhelm of Prussia. His mother was Victoria's eldest daughter Vicky while his father Crown Prince Friedrich Wilhelm (known as Fritz) was heir to the Prussian throne.
Little Wilhelm was a page boy at the wedding but he did not acquit himself well. He was dressed in Highland costume, complete with kilt and toy dagger. When he became restless during the ceremony his uncle the 18-year old Duke of Edinburgh told him to be quiet. At that point the defiant child drew his blade, threatened his uncle with it then bit him on the leg.
As a new two-part BBC documentary explains, it was to be the beginning of a long, tortured relationship between the future Kaiser of Germany and his British family that would help drag Europe into the abyss and cost 10 million lives in the First World War.
Wilhelm was born in January 1859 in a traumatic breech delivery that left him with a withered left arm. Disability was a badge of shame in fiercely militaristic Prussia and the boy was subjected to grotesque treatments in various bids to "cure" him. His right arm was strapped to his body in a vain attempt to force him to use the other one. When the imbalance in his neck muscles made his head twist, he was strapped into another restrictive machine.
As a result he grew up insecure and resentful, particularly against his English mother, whose obsession with his damaged arm reinforced his sense of inferiority.
For her part, the intelligent, highly educated Vicky had been married at 17 in an attempt by Queen Victoria and her husband Prince Albert, whose father had ruled the small German state of Saxe-Coburg and Gotha, to rescue Prussia from the excesses of German militarism. On the assumption Germany would soon be unified under Prussian leadership Vicky's job was to make sure the country became liberal and pro-British.
Her husband Fritz was a kindred spirit but their ideas were out of synch with the prevailing mood in Berlin. In 1862 the arch-conservative Otto von Bismarck became prime minister. Under his influence Prussia seized the Danish territory of Schleswig-Holstein, crushed the smaller German states and defeated Austria and France, achieving German unification by 1871.
FAMILY TIES: Queen Victoria with daughter Vicky, with the princes and Wilhem standing behind [BBC]
"The creation of the united Germany totally threatened the European balance of power simply because of the number of Germans, their strategic positioning in the middle of Europe and the fact that Germany had the most vibrant economy," says Professor Dominic Lieven of the London School of Economics. "In many ways it created in the middle of Europe a country which could potentially dominate the continent."
Within the new Germany Vicky was sidelined. "You cannot think how painful it is to be continually surrounded by people who think your very existence a misfortune," she wrote to her mother.
By this time her eldest son, who wore his withered hand in a glove and felt unloved by his mother because of it, had become fiercely hostile to everything his parents represented.
As Vicky wrote to Queen Victoria: "Willy is chauvinistic and ultra-Prussian to a degree and with a violence which is often very painful to me. He is turning into the archetypal Potsdam lieutenant with that evil admixture of a very loud mouth and a chauvinist's hatred and ignorance of all things foreign."
He was doomed to be the outsider among his European extended family. Princess Alexandra and her sister Minnie, whose husband would become Tsar Alexander III of Russia, spent idyllic summers at their father's summer home outside Copenhagen with uncles and aunts from across the continent.
Here Alexandra's son, the future George V, first met his Russian cousin Nicholas, the future Tsar who would die in the Bolshevik Revolution. Many other guests from the minor royal houses were also invited but the one relative who never came was Vicky's son Wilhelm. As a Prussian he was not welcome in humiliated Denmark.
To offset this exclusion he developed the habit of muscling into occasions, even at the expense of protocol. In 1887 he announced his intention to attend Queen Victoria's Golden Jubilee as Germany's representative, effectively leap-frogging his parents. The Queen was outraged at this discourtesy to her daughter and son-in-law and made it clear that they should be the senior German representatives instead. This simply fuelled Wilhelm's resentment. "It's high time that old woman died. One cannot have enough hatred for England," he wrote.
His grandfather died the following year. Fritz became Kaiser but he was suffering from throat cancer and died after just 99 days on the throne, which meant that the erratic, emotionally unstable Wilhelm now had absolute power at the age of 29.
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