Back when I were a lad, Coventry were very much English top dogs - players like David Duckham and Fran Cotton (I think) a bit later - and Bedford were always up there, with Northampton and Leicester making the East Midlands a rugby hotbed. Nottingham too, with players like Brian Moore, an England flanker called Rees, and the Scottish Dentist (Gray?), and Rob Andrew, I think.
With the beginning of league rugby (not to be confused with rugby league!) in 1987, then the ending of the Amateur regulations in 1996, some clubs were more prepared than others. The likes of London Welsh, once described as the best club team in the world, were caught out and dropped down the leagues. Wakefield (who had supplied the England captain for the 1987 inaugural World Cup) disappeared completely. So did Rugby, a bit later, conned by a businessman ex-player. they were never exactly a top-table club, but at least they existed...and now they don't.
The first ever rugby union 1st Division league table (apart from Oxbridge colleges, whose gentlemen were considered immune from the evils of rugby league) 1987/88: Leicester (champions), Wasps,, Harlequins, Bath, Gloucester, Orrell, Moseley, Nottingham, Bristol, Waterloo, Coventry (relegated) and Sale (relegated).
12 clubs, just 11 games (no home and away for several seasons yet). Leagues had arrived over the dead bodies of many a RU diehard, and there were fears of violent play out of all control. Completely groundless fears, of course.