>     The bootstrapping was interesting. BCPL had a bytecoded 
> representation
> of itself (descended like all such from the legendary 
> Burrough's B5000).
> One first wrote an interpreter for these byte codes, in this 
> case in NOVA
> assembler. This got BCPL running, but slowly. One then 
> started using BCPL
> to make a back end native code generator for the new machine.

It still is.  Richard's current BCPL distribution contains
INTCODE binaries for the compiler and INTCODE interpreter
written in portable C that gets you up and going, along
with a TRIPOS command interpreter and assorted utilities
in BCPL.  It also includes a few code generators (including
a quick-and-dirty 386 generator and a better Amiga-era 68000
generator) as examples.  Although on modern hardware even
the INTCODE interpreter is fairly snappy, 20+ INTCODE MIPS
or so.