Thanks for the memory, Albert!
I first saw those when trekking in the Simien Mountains in the Ethiopian Highlands, back in 2012. My guide at the time told me that they are only found at altitudes of over 4,000 metres (about 13,000 feet). They can grow as high as 10 metres (33 feet), and my guide also told me that, before the introduction of eucalyptus to Ethiopia, the stems were often used in the construction of the traditional dwelling houses.
I saw them again the following year, when I summited Kilimanjaro in Tanzania. And they are apparently also found on Mount Kenya, in neighbouring Kenya.
Although the Tanzanian and Kenyan giant lobelia belong to the same species (Lobelia deckenii), the Ethiopian one is a different species (Lobelia rhyncopetalum).
I certainly have photographs of the Ethiopian variety, and think I also have some from Kilimanjaro. Unfortunately, my main photo archive is on a hard drive that I am unable to access just at the moment.