"Well, that's another world saved...another one for your CV..."
It had been a tired comment from Sarah Jane Smith as she stood with the Doctor in the Tardis control room. Behind them lay their terrifying encounter with Sutekh the Destroyer where, as usual, the Doctor had prevailed, albeit by the skin of his teeth.
Sarah was surprised by his reaction. He stared at her intensely for a long time, almost scowling. She became uncomfortable.
"I-I'm sorry. What have I said?"
"There are people out there saving worlds all the time," said the Doctor. "They don't even know they're doing it."
"What do you mean?"
"You saw what the future held if Sutekh had won." snapped the Doctor. "I showed it to you, Sarah Jane. Maybe that wasn't enough." His hands worked the controls...
It was a beautiful autumnal day as they sat together on the small, grassy hillock. In the distance they heard a deep, throaty roar from the aerodrome as engines coughed into life and propellers carved the air.
A line of shapes kicked up dust as they bounced across the grass strip towards them. Sarah counted five.
"They called it the Battle of Britain," said the Doctor, discursively. "What do you know about it, Sarah?"
"The Second World War. When we stood alone in 1940. Against the German airforce."
"Very good. And if you had lost?"
The noise from the approaching aircraft was getting louder.
Sarah shrugged. The Doctor spoke quickly, ticking off the points on his fingers.
"Operation Sealion. The Germans invade. Britain is conquered. There would be no D-Day. Russia would fall along with the rest of Europe. The Third Reich develop atomic weapons and intercontinental missiles. It would result in something very similar to Sutekh's World."
They both stood as the five aircraft bounced into the sky and roared overhead, Merlin engines throbbing their unforgettable concerto. Sarah could clearly see the roundel markings on the underside of each gull-shaped wing.
She watched them climb into the distance. "My father was in the RAF during the war," she said in a small voice. "He would never tell me what he did, though..."
"Second from the left." murmured the Doctor, shielding his eyes against the sun.
Sarah cried as she watched the little machines fade into dots.
Off saving worlds.
This year we celebrate the 70th anniversary of the Battle of Britain.
"Never, in the field of human conflict..."