Waitaha Toa won the Wellington Hurdles decisively two starts back and he finished second to Joint Effort in the National two years ago.
Riddell has won the National on Just A Swagger (2005) and Just Not Cricket (2008) from 10 rides in the race.
Waitaha Toa did not race beyond July 2 last winter.
"He had a slight tendon tear and we put him aside as a precaution," Lisa Latta, his Awapuni trainer, said.
Waitaha Toa has had an extensive programme of flat racing and hurdling since May. Latta opted for a flat race in preference to the Sydenham Hurdles at Riccarton last Saturday to top off his preparation.
He ran Wanabefamous to a head over 1800m.
"He has come through the race really good," Latta said.
"Now it is a matter of jumping all those fences [14 brush obstacles over 4200m]."
Waitaha Toa is favourite at $2.80 in final field betting with the TAB, ahead of Wotabuzz ($3.20).
Wotabuzz gave a dashing display to win the Sydenham on Saturday under 65kg. He was not liable for a re-handicap and has a similar weight today. Hayley Curran (21), who rode Wotabuzz to post her fifth win, has retained the mount.
Honey, who ran third to Kid Columbus and Foremost in the National last year, is among three representatives for trainer Kevin Myers today. The others are Limberlost and Sea King, who led a vain chase after Wotabuzz in the Sydenham.
Stewart Moir, who escaped injury in a track work fall at Wingatui yesterday, has the mount on Cee Gee Jay.
Moir was easing down Bellonet after fast work when she dropped her shoulder and unseated Moir.
"It was just unexpected and I got some sand in my eye," he said.
Moir has chosen to ride Cee Gee Jay over High Forty. He has won three hurdles races on Cee Gee Jay this winter and two on High Forty. Both horses are trained at Wingatui by Brian and Shane Anderton.
Moir (31) returned to race riding this winter after surgery for bowel cancer last year. He underwent two operations. He finished second in the National Hurdles on the Anderton-trained Nicholman behind Counter Punch in 2007 and second in the National Steeple the following year.
The stable has won the National Hurdles with Bymai (1980) Lord Venture (1986) and Narousa (2001).
• Track conditions will determine the spring programme for Ocean Park, who won a trial at Te Teko yesterday.
"He is not a wet-track horse so if he looks like having wet tracks here, he could head to Australia earlier," Gary Hennessey, his trainer, said.
Ocean Park has been nominated for the triple crown races at Hastings, the Caulfield Cup and Cox Plate. He is at $9 in the Challenge Stakes (1400m) on September 1.
Winner of the Wellington Stakes last season, Ocean Park has not raced since since he finished second to Laser Hawk in the Rosehill Guineas in March.
• The Australian-owned Salomina is second favourite for the Prix de l'Arc de Triomphe after her win in the German Oaks, AAP reports.
She is raced by Luke Murrell and Jamie Lovett, of Australia Bloodstock.
They have German imports Lucas Cranach and Mawingo contenders for the major cups in Australia.
Salomina is from the same stable and by Lomitas, the same sire as last year's Arc winner, Danedream.
"According to the trainer [Peter Schiergen], she is more advanced than Danedream at the same stage of their careers," Murrell said.