  Virtually all binaries consisting of a white dwarf with a non-degenerate
companion can be classified as either close post-interaction systems (with
orbital periods of a few days or less), or wide systems (with periods longer
than decades), in which both components have effectively evolved as single
stars. Binaries with periods between these two extremes can help constrain
common envelope efficiency, or highlight alternative pathways towards the
creation of compact binaries. To date such binaries have remained mostly
elusive. Here we present three white dwarfs in binaries with evolved subgiant
stars with orbital periods of 41, 52 and 461 d. Using Hubble Space Telescope
spectroscopy we find that all three systems contain low mass white dwarfs
($\leq$0.4 M$_{\odot}$). One system, TYC 8394$-$1331$-$1, is the inner binary
of a hierarchical triple, where the white dwarf plus subgiant binary is orbited
by a more distant companion star. These binaries were likely formed from a
phase of stable but non-conservative mass transfer, as opposed to common
envelope evolution. All three systems will undergo a common envelope phase in
the future, but the two shorter period systems are expected to merge during
this event, while the longest period system is likely to survive and create a
close binary with two low mass white dwarfs.
