After two attempts I finally made it. Having completed Couch twice before, the 20 minute run did not cause me great worries, but my first attempt this time was during a Prom (Park) Run, and I was going much quicker than usual, and could not sustain a run at that pace for 20 minutes.
The second attempt earlier this week was again too fast, and I had to abandon. So this time, keeping in mind the frequent sage advice of Slow and Steady I went much slower. And finished the run with no problems, in fact I managed a three minute extra jog in the five minute warm down.
And then a real bonus - checking my times and distances for doing the same run in 2014 and 2017 I found that I had gone further and faster than in those years.
So, to those heading toward 5(3), this 71 year old made it with no problem once he screwed on his sensible Slower and Steadier Head - and so will you. There Is Nothing To Fear.......
Just edited to add photo and to say I felt so good after the run that I knocked out a mile walk straight after.... That afterglow is powerful stuff.....