Top of the table Doncaster weathered early storms - of the rugby and electrical variety - to stay on course for an instant return to the Championship.
First half tries from Michael Hills and captain Matt Challinor saw Knights recover from a slow start to lead 15-6 at the break.
Late scores from Bruno Bravo and player coach Glen Kenworthy then sealed a 12th straight league win at Castle Park this term.
A war of attrition against plucky Richmond was memorable for two things, firstly the extraordinary thunder storm that greeted the players almost from the moment they came out for kick off.
Secondly, the hard- earned victory rather epitomised Doncaster’s season; it was not pretty at times but they got the job done.
Following a freakish five-minute storm Richmond got to grips with the horrendous conditions first, breaking the deadlock from a routine Rob Kirby penalty before the fly half doubled his side’s lead with another kick from almost half way.
Bu Doncaster began to wrestle their way back into contention and gain a foothold.
Tyson Lewis latched onto a neat kick from Paul Roberts only for his try to be ruled out by the touch judge, before Roberts halved the deficit with a close range penalty.
Knights were beginning to enjoy more controlled possession and they made it count when Hills touched down following a catch and drive from a lineout.
And the hosts increased their advantage on the stroke of half time when Challinor, making his 100th Doncaster appearance, rounded off an incisive passing move to go in under the posts, with Roberts adding the extras.
Knights looked refreshed and resplendent in their red change kit for the start of the second half, following their soaking in the first.
Butagain it was Richmond who made the brighter start, Kirby reducing the deficit from a penalty just moments after hitting the post from a similar distance.
Roberto Santamaria was then sent to the sin bin for a dangerous tackle and the visitors had their tails up, but were soon reduced to 14 men themselves when Harry Edwards was shown a yellow card for killing the ball as Knights probed the Richmond try-line.
As a tight contest entered the final quarter there continued to be few scoring opportunities, until Richmond’s John Attlee was sin-binned for his illegal attempt to stop Doncaster’s drving maul - and eventually, following a series of resultant scrums, it was Bravo who broke from the base to put the game beyond Richmond.
Player coach Kenworthy then touched down to seal a four-try bonus point, driven over by more great work from Doncaster’s forwards, and Jamie Lennard kicked the extras.
Knights, three points clear at the National One summit, travel to Loughborough Students on Saturday.
n Knights: Woodhouse, Jarvis, Clark, Armitage, Lewis, Roberts (Lennard 66), Bravo, Sodini, Santamaria, Morris (Davies 50), Kenworthy, Challinor, Buggea, Hills, Planchant (Bergmanas 52). Replacements: Bryce, Flockhart.