Right, I've been running in ldwa events for over 20 years (including 2 hundreds), but as age catches up (I'm 64 next week) I have to say it is becoming slower, harder and more painful - there is little pleasure in training, it's simply a painfest! A knee breaking up has also set me back a couple of years, wear and tear.
So my first advice is if you are anywhere approaching my age, stick to walking and save yourself the pain + gain longevity in joints etc.

At 5ft6in and having the shortest legs on the field, I also suffer "leg envy" like yourself, but have still managed to scuttle along quite successfully over the years, following those long legged walkers that cover the ground so effectively - runners have the same advantage!

Running and walking use slightly different muscles, so however fit you are, you do need to train a little in the other discipline; runners are good at running but I have met very, very few that can walk sections at the speed of a good walker. Because they run, they never try to improve their walking and as a result are c**p at it, as a runner I always tried to practice my fast walking and it pays off.

Employ "Ruddles Rules" (named after a famous distance fell runner), ALWAYS walk any ups, even slight inclines, jog the flat and downs. I would add to start, that on the flats you pace yourself to jog/walk 50% max and see how it goes. The aim is to sustain a steady pace over the 25+ miles as walkers do, there is no point in blowing up after 20 and slowing down. Also when walking bits, concentrate on keeping your fastest walking speed going otherwise the beggars will catch you again if you slow a fraction.
I've just had a look back at some old walk certificates and I reckon I've lost about 1mph over 20 years - that is mainly rough hill events in Wales - but I am nothing like as fit now.

I would say give it a try and you will go faster, I would never say it is easier or better on your feet, but finishing near the front means you get the best fresh sandwiches and cakes + first at the bar. It is worth it.

I'm wondering whether running, or at least jogging or a similar light waddle, might be easier than walking on challenge events, especially for someone who, like me, has a very short stride. Guidance welcome.

Away from the LDWA I enjoy trail running, but on my four hundreds I've walked every step of the way (220,000 steps on the Dorset marshals' walk, my now-deceased Fitbit told me). I got terrible blisters in Dorset, and I'm wondering whether jogging might ease the pressure on my feet: harder landings, but less time in contact with the ground per stride.

But the real reason I ask is that at 5-foot three in height, I have to work very hard to maintain a brisk pace, and cannot keep up with a tall LDWA-type walker without trotting, except on steep uphills. On the other hand, my light weight (about 52 kg) and shorter limb length probably favour me when I run.

I'm aware of the danger of lactic acid build-up but I think that with four hundreds done, I can afford to take the odd risk now.

Can anyone advise on the relative merits of hard walking and light jogging on a challenge event?