Roughly speaking, in about the same situation: finding the modern equivalent of the open field (I’d pick a forest—nobody can bug every tree, and the canopy hides satellite visible- and most IR-snooping) for a face-to-face meeting. Mail back then wasn’t safe, even with couriers, until laws were passed that made casual mail-snooping by the government illegal. It seems to me (but I’ll defer to anyone who differs and actually knows) that rights regarding digital messaging are in a high state of flux right now, with regard to actual privacy vs. legal rights, and high-end cryptography with a great deal of care is the only way to make it more likely than not that long-distance communications are private.
And hey, the King only goes after the bad people, mostly, right? If you have no ill will to the Crown, they’ll have no ill will toward you, eh?