Proton Structure from HERA to LHC

The kinematic region covered by the LHC experiments probes low values of Bjorken-$x$. At the scale relevant for $W$ and $Z$ production the central rapidity region covers ${10}^{-3}<x<{10}^{-1}$. This means that it is the HERA data which give the most insight into the behaviour of parton distribution functions (PDFs) for the early phase of running at the LHC. The H1 and ZEUS experiments are combining their data so as to provide a legacy of HERA results. The present status of the data combinations and the impact of these data on our knowledge of parton distribution functions is explored.