Exercise is one of the legislated reasons, so that is good reason. Never in doubt or questioned. Being asked to account for the reasons for your being out is entirely right and justified when you shouldn't be without good reason. We are not living in normal times.
No, we're living in a state of perpetual fear driven by the media and fuelled by guesswork (you can only flaten a curve if you know when it started, we have no idea how long Coronovirus has been in the UK because all the people who we though died of flu back in December, January and early Febraury, are already burried/cremated so can't be tested to see if it was Coronovirus that they died from instead of seasonal flu, which has the same symptoms).
So, with all due respect,
1) I've practically lost my business - all future work cancelled, all existing contracts paused and outstanding invoices not being paid, even by big businesses that should know better as they ware receiving multi-million £ bailouts, the only help I'm going to get I won't see until June at the earliest.
2) I have lost my liberty, I am no longer allowed to leave the flat without a good reason, I am only allowed to do it once a day for exercise, and I'm not allowed to drive anywhere, even alone, to do it because of risks. It is not an exhaagerating to say that fun has been made illegal. Pretty soon we will probably be in the same position as the French, and not even be allowed to leave home without a permission slip.
3) Fairly soon we will likely be homeless because our savings will runout, and despite promising otherwise Boris f***** up the legislation so much that as one MP put it, it merely gives us more time to pack, yes I am aware that there is help available, and we are looking into this, but there is a huge backlog on applications.
I know none of the above is your, or any other members doing, but I hope you will excuse me for hanging on to the last semblance of normality that I have of still being free enough to walk down the street unharrased and not have to account for my actions because you or your colleagues are "just doing your job" - might want to look at a history book and rethink that line too (I know you haven't said it, but I have heard it said by others).
Nothing I've said is aimed at you personally, where I say you, I am talking in overall general terms of the predicament both the force, and the public find themselves in.
But before I get screamed at again by anybody for being hysterical and told to "get a grip this will only last three weeks", if you seriously believe these restrictions will be lifted then, then you are delusional, I'll happily apologise if I am wrong but I don't think I will be, and the Italian death figures are so high because the doctors have been ordered not to treat older people (age varies from 65 up depending on the region).