Londoners were already starting to queue up Friday outside Apple’s (AAPL) newest retail outlet — in Covent Garden — its fourth in the city and its 300th worldwide. The grand opening is set for Saturday at 10 a.m. GMT.

This is an Apple Store for the record books. Largest and most expensive. Longest Genius Bar. Biggest staff (300 employees). And most elegant interior, restored from its original Welsh stone and English oak, with exposed brick walls and two glass interior staircases.

The entire Fifth Avenue store in New York City would fit inside its three-story central courtyard.

Below: Two videos — one shot from the inside by Electricpig‘s James Holland, the other from the outside by ifoApplestore‘s Gary Allen, the dean of Apple Store reporters. Allen has flown to London the cover the event.

Inside:

http://www.youtube.com/watch?v=wkY0uJAq4Mo

Outside:

See also:

• Philadelphia finally gets its Apple Store
• Apple plants its flagship in Shanghai
• Parisians storm Apple’s newest store
• NYC’s newest landmark: The Apple Store
• Apple invades France
• Apple’s Munich opening is mobbed — in fullscreen panorama

[Follow Philip Elmer-DeWitt on Twitter @philiped]