Assuming the Queen of Marleybone is parallel to Queen Victoria, perhaps the Queen has gone to oversee the unrest in Kensington? After all, she was born in Kensington Palace.
Alternately, she might just be wary of seeing powerful wizards given the huge number of people who have tried to assassinate her.
And let's face it, she is from a long, long line of kings, whereas you and I are just wastrels found in faraway worlds along the Spiral. Would it not be unseemly for the Queen to be seen with commoners such as us? Maybe we should be asking for an audience with the Prime Minister instead. And then, given our service to the Crown, maybe we will someday be granted an audience with Her Majesty.