central baryonic disc and the dark matter halo. A large fraction of the halo stars in our Galaxy are the tidal remnants of destroyed dwarfs. Hence, to first order, the spin of the Milky Way stellar halo represents the net angular momentum of all of its past (stellar) accretion events.

The search for a rotation signal in the Milky Way halo dates back to the seminal work by [@frenk80]. The authors used line-of-sight velocities of the Galactic globular cluster system to infer a *prograde* (i.e. aligned with the disc) rotation signal of $V_{\rm rot} \sim 60$ km s$^{-1}$. A prograde signal, with $V_{\rm rot} \sim 40-60$ km s$^{-1}$, in the (halo) globular cluster system has also been seen in several later studies (e.g. @zinn85 [@norris86; @binney17]). However, the situation for the halo stars is far less clear. While most studies agree that the *overall* rotation speed of the stellar halo is probably weak and close to zero [@gould98; @sirko04; @smith09; @deason11a; @fermani13b; @das16], there is some evidence for a kinematic correlation between metal-rich and metal-poor populations [@deason11a; @kafle13; @hattori13] and/or different rotation signals in the inner and outer halo [@carollo07; @carollo10].

An apparent kinematic dichotomy in the stellar halo (either 