The December JBAA has an article on the curious star which may be Nova Leonis 1855 but, if so, it is a very peculiar quiescent nova. In particular the visible star is spectral type F and there seems to be no spectrographic evidence for either accretion or a companion, though there is strong evidence for a periodic variation in brightness of depth around 100mmag and period of 3.2 hours.
Something has been nagging me about this description for the last couple of weeks. It sounded familiar but I couldn´t put my finger on it. This evening I was browsing Burnham´s and inspiration struck. From a Wikipedia page:
Epsilon Aurigae (ε Aurigae, abbreviated Epsilon Aur, ε Aur) is a multiple star system in the northern constellation of Auriga. It is an unusual eclipsing binary system comprising an F0 supergiant (officially named Almaaz /ælˈmɑːz/, the traditional name for the system) and a companion which is generally accepted to be a huge dark disk orbiting an unknown object, possibly a binary system of two small B-type stars.
The period is vastly greater, around 27 years, but the features in common struck me.
Could U Leo be something similar but on a smaller scale? A dusty disk orbiting a white dwarf which itself is not currently accreting. On this model the disk would be inclined to the orbit of the two stars and precessing with a period of 3.2 hours such that regions of different density lie between us and the F star at different times.