"I have a eidetic memory," Mel says one day, out of the blue.
"Memory like an elephant," Donna answers automatically.
Mel gets an odd look. "Yes. Something like that. It's what my best friend always used to say."
"Fond of cliches, was she?"
"He, actually. Though mostly he was fond of mangling them."
Donna doesn't point out that the cliche is intact. Instead she asks Mel to pass the laser spanner.
If Mel has a memory like an elephant, then Donna has one like a sieve. Only the metaphor's wrong. A sieve has a lot of tiny holes: a sieve is almost nothing but holes. Donna's memory just has one big hole. A two-year sized one, in fact. Her first wedding disappeared down that hole. She wishes her second had. Things had gone bad with Shaun after they'd won the lottery. The money went to his head and he'd started having affairs with starlets. Donna had waited until after the divorce to have her own afffair and Mel wasn't exactly a starlet. She was older than Donna, for one thing. Donna wasn't sure exactly what Mel was, really, except bloody brilliant and unbelievably athletic. Oh, and a screamer. Definitely a screamer.
Mel told her once that she'd been a space pirate until she'd come home to pick up her mail and her no-good boyfriend had run off with their spaceship. (Donna didn't think about that much. It gave her a headache.) But before all that she had been a computer programmer. She was still a computer programmer, only now she was an computer engineer too. And so, somehow, was Donna.
There was a hole in her mind, but the memories lived on in her fingers. Donna had been fairly good with computers before her amnesia. Now she was quite frankly a genius. All she had to do was let her mind get pleasantly blank--and staring at Mel was definitely good for that--and let her hands move on their own. JUGGERNAUT was coming together at an astounding rate. And Donna's half of the lottery money definitely helped pay their expenses.
So here they were. Two middle-aged redheads assembling the world's most sophisticated supercomputer in a barn in Pease Pottage. And why not? It was as good a place as any for history to remember them.