London marathon bags

I want to have a change of clothes after the marathon. My options are:

• Take a bag to the mall the day before so it’s ready to collect when I finish the marathon

• Ask my wife to carry the bag and I find her after the run

Which would be the fastest/easiest thing to do? Obviously there will be a lot of runners and surely a lot of people queueing for their bags at the end.

But also, how easy is it to find your people after the run? Again, there will be a lot of people milling about.

Are there places where you can change after the marathon?