Another delay: call to Ancient Egypt

Today I got a distress signal from one of the automated time portal Guardian Sensors that were randomly scattered across space-time by the Timelords ages ago, and are questionably still functioning.  It honed into the TARDIS background signal and found me just as I'd finished preparing for the journey to find out more about the Time War.

Old-tech Timelords' Guardian Sensor comes a'callin' *

This beacon is calling me back to the Lighthouse of Alexandria, to the coast of Egypt.  I don't remember much about the Lighthouse, besides the fact that it was one of the Earth's Seven Wonders of the Ancient World, so I'll try to do some research :) as I follow the guardian's beacon back to its troublesome source.

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*Apologies and thanks to EntecMedia, whose gift box I used to pretend that it was the sensor.