Please read the disclaimer.
So you are going out for a longish training session, and you know you can walk in good technique for the distance required.
You can now start to turn these sessions into something that improves your lactate tolerance and your cruising speed, by making them a little more aerobically demanding.
To do this without leaving behind the people in the training group who are still working on their technique, you can do this by adding fartlek-type surges to your run, and at the end of each surge turning back to rejoin the rest of the group. Surges should be longer rather than shorter; should go to a definite landmark before you turn back, e.g a roundabout or a junction; they should of course be done maintaining good technique (i.e. no more surges if your technique is starting to fall apart).
They should be done at around your 10k race pace, which is normally around your lactate threshold pace. You should not need to recover much before being able to start another surge.
Pick a suitable stretch of road to do them on – i.e. not on narrow pavement in the busiest part of town, not in the slippy and lumpy bits of the Radley Lakes loop, not where you will have to press buttons for road crossings . . .
Eventually, if all the surges can join up into one, this will become a ‘lactate threshold’ or ‘tempo’ session. Once you’re approaching this, you will need to have another distance session, somewhat longer, in your training programme too.
Did you read the disclaimer?