As soon as possible, send a FAX to the German Embassy in London requesting urgent appointment for passport service, explaining your travel plans and ask for consideration. If you're in London, go to the embassy in person if it is allowed.

Depending on the resources they have, it might work out. But send them the fax as soon as possible......don't forget to add your contact info in the fax so they can reach you.

Lesson learned = When you're in a foreign country, always ensure you maintain valid passport. It is never good to leave things to the last minute.

good luck!