After a terrible first 20 minutes in their London one south clash at Trojans, Chichester surged back to win with free-flowing rugby and five tries before half-time - ending as 57-23 victors.
The final tally was nine tries and six conversions to two tries, two conversions and three penalties.
Trojans shook them and went 16-0 up but the Blue snake uncoiled and bit hard. Richard Adams collected 22 points to make 250 for his season.
Basingstoke also had a large win so with two games left the race for runners-up spot and a promotion play-off depends on Chichester gaining maximum points and Stoke being denied any in their last game away to champions East Grinstead.
There was rare sunshine and a very firm pitch to greet the travelling fans. The Blues were forced to make five changes but the squad looked strong enough.
Trojans rose from the bell with plenty of fight and charged down an Adams kick on the 22. A penalty for offside was slotted by scrum-half Lynch for a 3-0 lead.
Another penalty came as Chi hooker Giddings was sin-binned harshly for a first offence, going off his feet at a ruck. Lynch made it 6-0.
Chi finally got to the home 22 after ten minutes but a floated pass was well intercepted by lock Williams, who raced away to score under the posts at the other end.
One penalty was missed before Lynch made no mistake with a fourth and at 16-0 this was ominous.
Suddenly there was a dramatic change. Chi moved smartly to the right corner and lineout and drive put the energetic Giddings over, but the conversion was missed.
Chris Johnson barnstormed and good handling by Henry Anscombe, Jack Bentall and Sam Renwick settled Chi into their groove.
Giddings carried strongly and the ball was spun out for Renwick to pass to Tim Cook, joining on a great line from full-back. Adams kicked the first of his six conversions.
Chi were motoring and now had all the possession. Moses Kasujja and Johnson attacked and linked with the powerful Bentall and Cook in support. Lineout and drive held up, Kasujja picked up from the Chi scrum and fed winger Toby Golds to score at the corner.
Niall Goldie came off the bench and made an immediate impact. With good lineout won, the backs were sharp and a long pass from Adams found Renwick to stride over at the left corner, just managing to ground the ball before crossing the dead-ball line. Adams kicked a superb conversion from out wide.
With a bonus point for the fourth try in the bag and a 24-16 lead, Chi were in total command and forwards and backs were massing in attack. Jon Lindsay in the engine room was back to his best pre-injury form and Nick Blount was soaring in the lineout.
Adams rounded off the half with a brilliant solo try from 40 metres, his change of pace and swerve leaving tacklers floundering. Another conversion meant it was 31-16 at the break.
Goldie caught the Chi kick-off with his usual skill and Chi thrust left. A solid scrum led to the dynamic Kasujja breaking through, offloading to Johnson to score, but the big flanker pulled a hamstring as he went over.
Trojans arrived in Chi’s 22 after a long absence and won a scrum. As they broke out, Giddings infringed and was given a second yellow card so he had to leave for good. He was unlucky but it meant Blues were down to 14 men for 30 minutes.
Despite this, Goldie, Cook and Anscombe combined and were nearly across. A Blount lineout catch and controlled drive preceded the reliable Dane Gingell touching down for a try which was converted.
Another attack gave useful handling and passing practice with prop Nick Shopland joining in competently. Renwick went over but it was disallowed for a forward pass.
A Trojans flanker was sinbinned as they tried desperately to stem the flow. From a lineout Kasujja joined the backs and passed to Renwick to complete his double. It was converted.
Bentall had a spectacular run from near his own posts, beating numerous attempted tackles to reach the halfway line. On they went with Anscombe and Renwick threatening.
Second phase gave Adams the chance to carve his way through and score from 25 metres. The conversion took the score to 57-16. A few minutes of scrappy play followed before a Ben Robson score was ruled out for a forward pass. To their credit, Trojans kept trying and were rewarded in the last minute with an excellent try by Williams, who ran hard with sidesteps along the right wing before Lynch converted.
The Blues’ head coach Rob Lawrence said: “We were very slow out of the blocks but in the 15 minutes before half-time we won it with excellent running rugby. Our discipline remains a problem, though.”
This was Chi’s 20th win of the season and their ninth double. This week, in their final home league match, they host Gosport, who are battling to avoid the third relegation spot. All support welcome at Oaklands Park - kick-off 3pm.
CHICHESTER: Shopland, Giddings, Davies, Lindsay, Blount, Dickin, Johnson, Kasujja, Anscombe, Adams, Robson, Bentall, Renwick, Golds, Cook, Gingell, Goldie, Seaman.