based on the shape of the pen and the nib, and on the band around the base of the cap, I think that HM is using a Parker Sonnet.
From the colour of its grip section, I think that it is actually one of the less-expensive Sonnets, which ordinarily comes with a steel nib (although one can buy a rhodium-plated 18 carat gold nib and screw it in to the pen).
Curiously, I am currently thinking of buying that exact model of Sonnet.
One UK website that sells Sonnets (and in all of the nib sizes that Parker offer!) can be found here:
On the left of that page one can set filters for pen style (i.e. fountain pens), colour, nib material, price, etc.
I hope that helps.
Edit to add:
If you are thinking of buying one, I feel that I should also let you know that during my time on here I have seen many complaints about Sonnets being ‘temperamental’ pens, and that they tend to dry out if left unused.
There is a discussion of this problem , and some ways to fix it, here:
I have also posted threads in the FPN Parker forum and the FPN Waterman forum to ask for advice on choosing between a Sonnet and a Waterman Carène.
I only started those threads two days ago, but some of the replies are already re-reporting the drying-out problem.
The Sonnet is available in many different finishes, and in many different nib widths, but that beauty is of little use if the pen is unreliable.
The consensus so far seems to be that if you ink-up a Sonnet in the morning and then write with it all day long it is a really nice pen. But also that it will start to dry out even overnight, and if left for even a few days so much water evaporates from the ink inside the pen that the ink will change colour. Which is annoying, but not as annoying as the fact that the ink is effectively ‘wasted’, and you will need to refill the pen more often.
This ability to get this kind of ‘inside information’ from people who have owned a particular pen for some time - and their generosity in sharing their experiences - is one of the things that make being a member of this community such a great experience.
Edited by Mercian, 23 January 2020 - 13:22.