London marathon

My brother & i are doing our first marathon together at next weeks London marathon. We train together have done lots of races together but have been allocated different start areas! Anyone know if the marshalls really do check you're at the correct start area?

If you're genuinely on different starts (red/blue/green), yes they check the colour of your number and only admit someone with the right coloured number to the start in question. If you mean you're on the same start but different pens, you're allowed to move down a pen i.e. you can both start in pen of the slowest runner. All of the starts merge at mile 3 so you could try and meet up there or somewhere a bit further along the course, but I'm sure you'll each meet other runners on your start and have a great time running with others.

Yes, you cannot start at the wrong start, unless you are prepared to wait until everyone else crosses the start line and then tag in on the back.  That will mean that you will have to work your way through all the slow runners, walkers and those in costumes though.

Running a marathon is tough enough without the added stress of trying to outwit the marshals, who are on the lookout for anybody trying to get into the wrong enclosure, let alone the wrong starting pen. My wife and I are aiming to run the same time, but are starting at blue and red starts and planning to meet up at the 4 mile mark after the merge. It would be nice to start together, but this is the next best thing, assuming we both stick to our pace plan and manage to cross the line in approximately the same time. It should help that we'll both be starting in the first pen at each start, because the race will be less horrendously crowded after 4 miles at 6:45 pace.

If you are in the main body of the race, say around 4 hour pace, it is like trying to find a needle in a haystack spotting somebody, unless you are both 7 foot tall or something.
Good luck to you and your brother.