  The Liverpool Telescope is one of the world's premier facilities for time
domain astronomy. The time domain landscape is set to radically change in the
coming decade, with surveys such as LSST providing huge numbers of transient
detections on a nightly basis; transient detections across the electromagnetic
spectrum from other facilities such as SVOM, SKA and CTA; and the era of
`multi-messenger astronomy', wherein events are detected via
non-electromagnetic means, such as gravitational wave emission. We describe
here our plans for Liverpool Telescope 2: a new robotic telescope designed to
capitalise on this new era of time domain astronomy. LT2 will be a 4-metre
class facility co-located with the LT at the Observatorio del Roque de Los
Muchachos on the Canary island of La Palma. The telescope will be designed for
extremely rapid response: the aim is that the telescope will take data within
30 seconds of the receipt of a trigger from another facility. The motivation
for this is twofold: firstly it will make it a world-leading facility for the
study of fast fading transients and explosive phenomena discovered at early
times. Secondly, it will enable large-scale programmes of low-to-intermediate
resolution spectral classification of transients to be performed with great
efficiency. In the target-rich environment of the LSST era, minimising
acquisition overheads will be key to maximising the science gains from any
follow-up programme. The telescope will have a diverse instrument suite which
is simultaneously mounted for automatic changes, but it is envisaged that the
primary instrument will be an intermediate resolution, optical/infrared
spectrograph for scientific exploitation of transients discovered with the next
generation of synoptic survey facilities. In this paper we outline the core
science drivers for the telescope, and the requirements for the optical and
mechanical design.
