R Studio cannot connect to R

Edit: I have resolved it by reinstalling R and RStudio

I've had RStudio running with no issues for a while but now have an issue where it is unable to connect to R on launch.

This seems to have been caused at some point when installing some packages, Rmarkdown and Shiny I believe, maybe also ggmap. R aborted and now when I launch RStudio it doesn't connect.

I'm able to launch R console OK. I've also tried resetting client state as per guidance but no joy. I've also tried removing the above 3 packages from the R console but no joy. Nothing else has changed in the setup.

This is on Windows 10. If I start RStudio holding ctrl then I can connect to the 32bit version of R and RStudio opens ... so presumably something is wrong with the 64bit version even though it opens OK. I do not have admin rights on this machine so am now in a queue for support to try and uninstall/reinstall. If anyone has any better ideas please let me know

Any ideas?