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We report the discovery of an esdL3 subdwarf, ULAS J020858.62+020657.0, and ausdL4.5 subdwarf, ULAS J230711.01+014447.1. They were identified as L subdwarfsby optical spectra obtained with the Gran Telescopio Canarias, and followed upby optical-to-near-infrared spectroscopy with the Very Large Telescope. We alsoobtained an optical-to-near-infrared spectrum of a previously known L subdwarf,ULAS J135058.85+081506.8, and reclassified it as a usdL3 subdwarf. These threeobjects all have typical halo kinematics. They have $T_{\rm eff}$ around2050$-$2250 K, $-$1.8 $\leq$ [Fe/H] $\leq -$1.5, and mass around0.0822$-$0.0833 M$_{\odot}$, according to model spectral fitting andevolutionary models. These sources are likely halo transitional brown dwarfswith unsteady hydrogen fusion, as their masses are just below thehydrogen-burning minimum mass, which is $\sim$ 0.0845 M$_{\odot}$ at [Fe/H] =$-$1.6 and $\sim$ 0.0855 M$_{\odot}$ at [Fe/H] = $-$1.8. Including these, thereare now nine objects in the `halo brown dwarf transition zone', which is a`substellar subdwarf gap' that spans a wide temperature range within a narrowmass range of the substellar population.

Primeval very low-mass stars and brown dwarfs - III. The halo transitional brown dwarfs