Penelope Standish is an agent with MI6.
The action that we follow her on takes place during the second half of the 1950s. Our introduction to her comes in a set of adventures about an American agent with the CIA, Lucas Hamilton. In the first of those tales, her role is extremely small and if there was anything more to her than the fact she was "the long British Student Ambassador" on a sojourn to Berlin along with a small number of American college students, it was not even hinted at. In fact, when we first meet her the initial mention of her, other than the color of her hair, which is red, is that she was "talking non-stop" to a friend. That, and she seemed at times to just take up space, as if an extra in a motion picture.
Back then she was described by Hamilton as being "a little too plump, a little too talkative, a little too eager to make friends, with hair far too red." That changes drastically in the second Lucas adventure, taking place later that year, when we are told, again by him, that "She had changed a great deal, slimmed down, toned up, and let her hair return to its natural auburn color; and tonight, in her 'little black dress', she was quite alluring, but still, a little too friendly" (Hamilton being naturally suspicious of everyone.)
While she was largely backdrop in the first appearance, she plays a major role in the second and shows over and again that she is a very good, albeit still fairly new, operative. She shows her worth several times to Hamilton in that exciting escapade they had in South Africa, and he to her, including being able to put down an enemy quickly and efficiently when needed. Her professional star might have really shown as a result of their work had it not been for a misogynistic boss who had no use for women in MI6 and even less for those who "went around ... shooting people", even if said people were MI6 traitors. And being half Irish did not help matters as tensions between England and Ireland were again getting heated.
Where she really would come into her own, though, is in the solo adventure we are allowed to follow shortly thereafter. When she gets transferred to Berlin, her abilities as an operative really come out.