During a slow start for the hosts, winger Jake Lloyd crossed for Blackheath after just two minutes, but Ionians were quick to respond with centre John Allott scoring and Greg Lound adding the extras to level the scores.
Lound’s penalty on 18 minutes gave Ionians the lead and, despite falling behind to a Harry Bate try three minutes later, the hosts would lead 18-14 at the break. First Lound scored with another penalty before back row James Sanderson went over.
Blackheath started the second half in similar vein to the first, Leo Fielding’s converted try putting them ahead on 42 minutes, but an impressive final 10 minutes from the hosts saw them rally to take the victory.
Centre James Tincknell went over to put the hosts back in front before winger Sam Wilson’s converted try two minutes from time secured the bonus point win.
In the battle of the bottom two in National Two North, it was Wharfedale who boosted their survival hopes after picking up an important 16-10 home victory over Yorkshire rivals Sheffield.
Back row Josh Burridge celebrated his 100th league appearance for the hosts by opening the scoring with a try on 26 minutes, before Sheffield hit back with a penalty to make it 5-3 at the break.
The visitors hit the front five minutes into the second half with a converted try, but hooker Dan Stockdale’s try levelled the scores at 10-10.
Two second-half penalties would prove to be the difference though with Wharfedale leapfrogging their opponents in the table.
Scrum-half Joe Rowntree starred for Otley in the day’s other Yorkshire derby, kicking 17 points in their 22-18 victory on the road at Huddersfield.
Rowntree kicked his first penalty before convering second row Brett Mitchell’s try early on.
Back row Nick Sharpe crossed for the hosts with Harry Davey adding the extras to cut the lead to three points, a margin that remained at the break after Davey and Rowntree traded penalties.
Substitute Ben Morrill’s try early in the second half put Huddersfield ahead, only for another successful kick from Rowntree to put the visitors one point to the good at 16-15.
Adam Blades then saw yellow for the hosts, Rowntree kicking two more penalties to secure the win.
Sheffield Tigers were beaten 36-5 at home against second-placed Hinckley, right winger James Martin scoring two of the visitors’ five tries.
Harrogate moved fourth in the North Premier league, surviving a late comeback to claim maximum points in a 30-23 victory over Birkenhead Park.
Both back row’s Guy Coser and Martin Dodds scored tries for the hosts, stand-off Luke White adding eight points with the boot to put the hosts in control at 18-6. Further scores from winger Olli Rosillo and prop Harry Butler wrapped up the bonus point for Harrogate, who held on despite two late converted tries for the visitors.
Hull’s game at Lymm was postponed due to a waterlogged pitch.
In North One East, leaders Driffield held on to a 10-9 victory at home to Alnwick after the visitors missed a drop goal attempt in the final minute of play.
West Leeds were 43-17 winners in their Yorkshire derby clash with Cleckheaton.
Full-back Danny Booth scored two tries, and others came from centre Sam Neave, scrum-half Joe Bedford, prop Dwayne Smith and hooker Steve Anderson, with Dale Breakwell kicking five conversions and a penalty.
Elsewhere, Bridlington are level with West Leeds on points after beating strugglers Dinnington 22-7, and Bradford and Bingley battled to a 36-30 win over bottom club Northern.