I've used left luggage several times at Heathrow, and I have found them to be efficient and they look secure enough. I wouldn't leave real valuables (camera stuff) with them, but I leave everything else. You can lock your bag with small luggage locks (ADVISABLE!!!) for flights once you leave the US, too. For checked bags, you'll have to get those hardware-type plastic ties or (Better) the numbered plastic ones from Travelsmith or Magellans or a travel shop). I'd advise using those even if you are using a TSA approved lock. )Anyway, if you are flying Business, you can leave your bags at the Bus Class BA lounge, which is very secure. But be careful about how much time you actually have in London. You want to get back to the airport 2 hours before flight time, its pretty much an hour in/out from Heathrow, and you will have to clear customs and immigration both ways--add an extra hour for that. The lines to do this can be quite long, both ways. So you only have 3 hours MAXIMUM that you can spend in London...personally, I'd do this on the way back from Africa, but just to be safe and rested, I'd stay at Heathrow and relax on your trip to Joburg. (There's actually lots to do there...it's like a shopping mall, with decent restaurant options, even a place you can arrange a shower and a nap (for a fee).
I've tried to learn from how wrong I was about the bud vase. I look for "bud vase features" when I'm thinking about designing products. What's a bud vase feature? Here's my definition:
A "bud vase feature" is functionality outside the core purpose of a product that evokes positive emotion about the product, and allows the user to express their personality or character in their use of the product.A bud vase doesn't make the Beetle drive any faster, and it may even marginally reduce the safety of the car. But it makes the driver happy every time they get into their car. Of course you want your product to compete with other products in all the standard ways -- price, performance, quality. But to draw your users into falling in love with your product, look for a bud vase.