Context : Radio galaxies classified as X-shaped/winged , are characterised by two pairs of extended and misaligned lobes , which suggest a rapid realignment of the jet axis , for which a potential cause ( including binary supermassive black holes , a black hole merger , or a Lense-Thirring precession ) is still under debate .

Aims : Here we analyse the complex radio structure of 3C 293 winged source hosted by the post-merger galaxy UGC 8782 , which uniquely displays a significant asymmetry between the sizes ( and therefore the ages ) of the two pairs of lobes , indicating that an episode of jet realignment took place only very recently .
This allows us to tightly constrain the corresponding timescales , and therefore to discriminate between different models proposed for the formation of X-shaped radio galaxies in general .

Methods : Based on all the available and carefully re-analysed radio data for 3C 293 , we have performed a detailed spectral modelling for the older and younger lobes in the system , using the existing evolutionary DYNAGE algorithm .
In this way we derived the lobes ’ ages and jet energetics , which we then compared to the accretion power in the source .

Results : We found that the 200 kpc-scale outer lobes of 3C 293 are \sim 60 Myr old and , until very recently , have been supplied with fresh electrons and magnetic field by the jets , i.e. , jet activity related to the formation of the outer lobes ceased within the last Myr .
Meanwhile , the inner 4 kpc-scale lobes , tilted by \sim 40 \degr with respect to the outer ones , are only about \sim 0.3 Myr old .
Interestingly , the best model fits also return identical values of the jet power supplying the outer and the inner structures .
This power , moreover , is of the order of the maximum kinetic luminosity of a Blandford-Znajek jet for a given black hole mass and accretion rate , but only in the case of relatively low values of a black hole spin , a \sim 0.2 .

Conclusions : The derived jet energetics and timescales , along with the presence of two optical nuclei in UGC 8782 , all provide a strong support to the Lense-Thirring precession model in which the supermassive black hole spin , and therefore the jet axis , flips rapidly owing to the interactions with the tilted accretion disk in a new tidal interaction episode of the merging process .
We further speculate that , in general , X-shape radio morphology forms in post-merger systems that are rich in cold molecular gas , and only host slowly spinning supermassive black holes .