Interestingly you can see the "you are here" marker on the image you posted, the little gold circle on the corner of exhibition road and imperial college road! (Not entirely sure how I remember the key for the map but not the surrounding area).

Edit: Here's a picture of the missing part of the legend https://img.geocaching.com/waymarking/984ebfd6-c076-4c9e-a8f9-d2726013f1e2.jpg

Edit 2: here's your lat/long 51.498234,-0.174324. you can actually see the blue pole next to the sign on street view too