Despite being absent from the racecourse since February of last year, the seven-year-old has been towards the head of ante-post lists for a while.
“You don’t like losing horses like him to injury but he is back now and hopefully as good as he was,” said Thornton
“He feels like he is at home but there are question marks.
“There is the long lay-off and always a slight one whether a horse retains its ability after injury.
“He was a very good novice and I can remember when they said he was not running in the RSA Chase I was absolutely mortified.
“He was one of my best chances at the Festival at the time.”
Invictus is one of 21 horses declared for the Hennessy.
Rocky Creek, trained by Paul Nicholls, is another who has had the Hennessy as a long-term target.
David Pipe’s Our Father and the Nicky Henderson-trained Hadrian’s Approach are other leading contenders, with Jim Culloty’s RSA Chase winner Lord Windermere heading the Irish challenge.
Willie Mullins has not declared Vesper Bell or On His Own – the only two withdrawals – but does saddle major contender Prince De Beauchene and outsider Terminal.
Malcolm Jefferson’s Cape Tribulation heads the weights on 11st 12lb, just ahead of the Venetia Williams-trained Katenko. Williams is also responsible for Houblon Des Obeaux.
Other candidates include Merry King, Highland Lodge, Super Duty and 2010 Cheltenham Gold Cup hero Imperial Commander.
Meanwhile, My Tent Or Yours heads a field of eight for the StanJames.com Fighting Fifth Hurdle at Newcastle tomorrow.
His main rival is expected to be Melodic Rendezvous. Jeremy Scott’s stable star missed the spring festivals after making a bright start to his hurdling career, which included success in the Tolworth Hurdle at Sandown in January.
John Ferguson’s Cotton Mill, fourth in the Elite Hurdle, again takes on Melodic Rendezvous.
Alan King’s Grumeti returns after a lengthy absence, while Nicky Richards saddles Duke Of Navan.
John Quinn, triumphant 12 months ago with Countrywide Flame, bids for back-to-back victories with the progressive Cockney Sparrow.
Completing the line-up are Rock Relief and Stormy Weather.