The story so far: Everything is being eaten by a cloud of fire. Humans are a dog’s best friend. A skull-faced couple are making people vanish in a puff of smoke and the TARDIS is developing black marks like the liver spots on your grandfather’s hands.
Enter a particularly brutal army of Sontarans, who no longer look diminutive or cute. They look like skinheads made of potato who are ready to do some serious damage.
Here are a few things that may aid your enjoyment, the next time that you watch "War of the Sontarans" from the latest season of Doctor Who:
1. The Crimean War was the one of the first post-industrial global clashes between empires. France, Britain, Sardinia and the Ottoman Empire on one side; Russia on the other. Across Europe and the Middle East, both sides benefitted from the technological advances of the Industrial Revolution, including railways, telegraphs and photographs.
2. This is not the first time the Doctor has visited that conflict either. During his visit to Victorian London in “The Evil of the Daleks,” the Second Doctor mentioned having some firsthand experience, while some of the soldiers involved in the war were kidnapped to become active participants in his final adventure, “The War Games.”
The siege of Sevastopol was the setting of a Seventh Doctor audio adventure which features Florence Nightingale (“The Angel of Scutari”), and the Twelfth Doctor assisted Mary Seacole in fighting off alien infections in the audio story “The Charge of the Night Brigade.”
3. Speaking of which, there are references to the epic poem “The Charge of the Light Brigade” by Alfred, Lord Tennyson, in the script. Not least when the Doctor instructs Mary Seacole to go “half a league onward,” a line that ends "all in the valley of Death rode the six hundred."  
The poem – which was published only six weeks after the charge took place, during the Battle of Balaclava on October 25, 1854 – is about brave soldiers marching towards certain death. The British light cavalry were instructed to stop Russian troops from seizing guns from captured Turkish positions, but this was miscommunicated and the Light Brigade found themselves riding into battle against a well-prepared artillery battery, capable of issuing a barrage of direct fire. The British retreated, but not before having to withstand many casualties and for little gain. The parallels with Logan’s attack on the Sontarans are bleak and plain.
4. This is the first Sontaran story to introduce a new chant. We all know “Sontar-ha!” as their rallying cry, but “Sontar-ho!” – as heard when Skaak executes Svild – is a new innovation.
5. When Skaak says, "This planet has defied us ever since the great Commander Linx first staked his claim in the ground of its feeble soil," he’s referring to events from the very first Doctor Who Sontaran story, “The Time Warrior,” in which the Third Doctor and Sarah Jane Smith met Commander Linx in medieval England.
6. Similarly, when the Doctor refers to herself as “former President of Gallifrey,” it’s a nod to “The Invasion of Time,” during which Sontaran forces invade her home planet. Rather unfairly, the invasion took place just after the Fourth Doctor, who had claimed “the inheritance of Rassilon” and “the Presidency of the Council of Time Lord” on arrival in Gallifrey, had banished an invading army of Vardans.
7. The Ravagers, Swarm and Azure, had originally been filmed arriving in the Temple of Atropos and surrounded by masked Ravager guards, but they were cut out of the final edit.
8. It’s true that Mary Seacole set up her British Hotel behind the lines during the war and nursed injured servicemen back onto their feet. She had to travel independently to the nursing teams supplied by the British War Office, as her help had been refused. As a British-Jamaican businesswoman of independent means, she invested her own money into providing care. Recovered soldiers and their families received this gesture so warmly that when she ran out of money in 1858, after the war was over, they helped to arrange a four-day-long fundraising gala on the banks of the Thames in London. Around 80,000 people came, including members of the royal family. Her notoriety may have dipped in the next 100 years – especially compared to that of her fellow Crimean medical veteran Florence Nightingale – but more recently her reputation has been rightfully restored as a medical pioneer.
9. If you feel like you’re familiar with the voice of Sara Powell, who plays Mary Seacole, it may be because she has a long history with Big Finish productions. Her resume includes adventures with the Fourth Doctor (Emma Fremantle in “The World Traders”), the Seventh Doctor (Contessa in “Vanguard”), River Song (the PA in “World Enough and Time”), and Jenny, the Doctor’s Daughter (Queen Minaris in “The Death of Peladon”).
10. There’s an exchange between Dan and his parents that comes from a very specific sort of local Liverpudlian knowledge. Eileen is explaining that a “fella in Birkenhead” found out you can stun a Sontaran by whacking their probic vent with a mallet. Neville explains that he was drunk, and Dan and his dad share a knowing nod, “Birkenhead.”
Birkenhead is a town on the opposite side of the River Mersey to the city of Liverpool, on the Wirral Peninsula. There has been a ferry linking the two settlements since around 1150, when monks at the Benedictine Priory at Birkenhead rowed passengers to and from Liverpool. And this is the “Ferry Cross the Mersey” as made internationally famous in the 1965 hit single by Gerry and the Pacemakers.
In the late 20^th century, port activity – and therefore employment – in the area suffered a severe decline, with accompanying social problems, which is why it’s likely that this would be the place where a drunk bloke might try hitting a Sontaran with a mallet, just to see what would happen.
What's your favorite moment from "War of the Sontarans"?