Hello! So, first things first. How do you fit the training in around the day (and night) job, and family life? I keep trying to get Yvette and the children to come out running with me, but without success so far. So it's a struggle – and, like most runners, I wish I could fit in more miles. I started training last summer and tend to do a long run every Saturday or Sunday morning and a short run and a step/circuit once a week before work.
You've done the marathon a few times already. Do you swear every year will be the last? Yvette says this third London Marathon is my last … We'll see. I've raised over £130,000 so far for two great causes: Action for Stammering Children and Whizz-Kidz. They both do brilliant work giving children help and confidence, which makes it worthwhile keeping going. And I've still not managed a sub-five hour marathon – so far it's been 5hr 31min (bad ankle) and 5hr 13min (lingering flu). So I'm hoping this year's the year. But would I then quit? Possibly …
How much rivalry have you got going on with your fellow MP runners? On the day, everyone is fabulously supportive – the crowds and fellow runners. But my shadow cabinet colleagues – Andy Burnham, Sadiq Khan and Jim Murphy – are all getting a bit competitive! They're all pledged to beat my time, which they will. But it's the fundraising that counts for me, and there they've got some catching up to do.
Where is your favourite place to run? I have done most of my training over the past few years running around Pontefract race track. But I also really enjoy running along the Regent's Canal through London Zoo.
Do you remember your first ever race? Kids' race? Egg and spoon at Bawburgh primary, Norwich, aged four. But my first proper distance race? A cross-country run around Wollaton Park in Nottingham.
How old were you, and how did you fare? I was 12 and I led for the first mile until I ran out of puff and was passed by almost everyone else. A classic schoolboy error – never go too fast at the start …
What's your greatest running achievement? Definitely completing my first London Marathon in 2012. The first is the toughest mentally, and it was really tough.
When someone asks for a training tip, what do you tell them? I am more likely to be asking than telling. But the most important thing I have learned is that you have to drink much more than you think you need to. It's very easy to dehydrate on a long and lonely training run.
Do you like a running gadget? If so, what's your favourite? I have a Garmin wristband digital tracker which I always wear. But I also like wearing fluorescent yellow gloves. Taking them off and putting on again a few times during a long run is very therapeutic.
Do you run to music? Never. I tried it, but I found the headphones hard to keep in and the noise really annoying. I enjoy the silence and solitude of running alone and love to look around as I run.
What's your favourite post-race indulgence? A Double Decker.
What is the worst thing about running? The first two and a quarter miles of any run. However many times I've done it, my body always screams out: 'Why is this happening?'
And the best? That moment soon after mile two when my breathing slows, my heart rate eases, the endurance gear kicks in and I think: 'Right, we're off'.
What do you eat on the morning of a race or a long run? A bowl of muesli and granola with extra raisins, a good 90 minutes before I start. On marathon days, I will add some chopped banana.
What's the furthest distance you've ever run? 26.2 miles!
If you had to choose who to watch, would it be Mo Farah or Usain Bolt (and are you secretly rather annoyed that running the marathon means you can't watch Mo's debut this year)? Definitely Mo – I would love to watch his start live, but to be running in the same race as him is rather magical.
Who is the greatest runner ever? Once again Iva Barr is also running for Whizz-Kidz – it will be her 16th marathon and she's aged 86! Now that's pretty great, don't you think?
• You can sponsor Ed Balls's London Marathon run for Action for Stammering Children and Whizz-Kidz at justgiving.com/teams/EdBalls2014