If you have 6 hours or half a day to spend in Outer London, here are some suggestions:
1. Visit the famous Wembley Stadium - home to the England national football team and host to various concerts and events. It would take approximately 1-2 hours to tour the stadium.
2. Take a stroll through the beautiful and historic Kew Gardens. Explore the different themed gardens and the iconic glasshouses. It would take approximately 2-3 hours to fully explore the gardens.
3. Head to the riverside town of Richmond and enjoy a leisurely walk along the Thames Path. Take in the stunning views of the river and visit some of the town's quaint shops and pubs. This would take approximately 1-2 hours.
4. Visit the famous Sherlock Holmes Museum on Baker Street. Immerse yourself in the world of the famous detective and his sidekick Watson. This would take approximately 1-2 hours.
5. Explore Camden Market, a vibrant and eclectic assortment of street food, vintage clothing and unique gifts. This would take approximately 2-3 hours.
Depending on how long you decide to spend at each location, you could potentially visit two or three of these places within your 6-hour timeframe.