Aye, I think it's the protagonist from The Great Game.
Yeah, it's Charlotte Hemmings the war photographer, the PoV character of
The Great Game. Hobb's End (of quasi-Quatermass infamy) Tube Station was where Robert Autumn, the protagonist of the original
Scarlet Traces that ran/was reprinted in the Meg had his underground hideout. That's what she's looking for.
We're up against that old chestnut of long-running stories and whether every tale should be self-contained in 5- or even 60-page chunks. Given Scarlet Traces is a long-running alternate history stretching from the end of the 19th C to the 1970s (so far), losing the sense of decades passing by discarding older characters would be a bad idea.