Don't think yours is H. flava. As far as I know H. flava always has yellow corona-lobes. Not shure what your plant is, need a good close-up of the centre of the flower to tell more. Might be H. officinalis ssp delaetiana.

The plants are: Socotrella dolichocnema, Orbea gemugofana and Orbea tubiformis.

... and the third one:

.. and the second one:

On Saturday 20th of June I will give a presentation on Stapeliads at the Zone 19 Symposium (Manchester). These are a few beauties that will be included in my presentation.

Yes, there is a pretty smell in my greenhouse right now!

Night flowering cacti have 'stunning' flowers. This one is in flower right now. Not sure about the name but looking into the New Cactus Lexicon Hylocereus ocamponis does not seem to be a bad quess

That is a huge bowl Mike! It takes up a lot of space so I woud have divided it into smaller pieces and repotted it long ago. Not yet many Stapeliads in flower right now but this small one from Socotra, Socotrella dolichocnema, has started flowering.

In flower today this Matucana myriacantha. An advantage of these flowers is that they are still open when I return from my work at the end of the day.

Yes, it is!