Problem installing Enviro software on Pi zero

I have tried both methods of installation with similar results. I get a series of error messages which endwith the following

No package ‘libffi’ found
c/_cffi_backend.c:15:10: fatal error: ffi.h: No such file or directory
#include <ffi.h>
^~~~~~~
compilation terminated.
error: Setup script exited with error: command ‘arm-linux-gnueabihf-gcc’ failed with exit status 1
Setting up i2c and SPI…

although it then appears to finish normally.
I cannot see any reference to i2cdevice in the error messages