The gelding, who officially turned 14 on January 1, recorded the biggest victory of his career in the galliardhomes.com Cleeve Hurdle back in 2014, when he defied his 66/1 starting price to defeat At Fishers Cross by a short-head with four-time Stayers' Hurdle hero Big Buck's back in third.
Knockara Beau has run four times previously in the Cleeve Hurdle. As well as winning in 2014, the son of Leading Counsel was also runner-up in 2011 and fourth in both 2013 and 2016. He has also recorded some fine efforts over fences, most notably when sixth, beaten under 20 lengths, in the 2012 Timico Cheltenham Gold Cup.
He made his first appearance this season at Carlisle on December 11 when taking third under 11st 2lb in a series qualifier for the Pertemps Final at The Festival.
Czech-born Jan Faltejsek, Knockara Beau's regular jockey, is booked for the ride once again.
Charlton, who is based at Stocksfield in Northumberland, said today: "At the moment, I would say Knockara Beau is 99 per cent certain to go for the galliardhomes.com Cleeve Hurdle. I would love it if it rained very hard and we would have to rethink if the going was on the faster side of good.
"The horse is absolutely fantastic and in great form. He isn't actually 14 yet but you wouldn't think he is going to be 14 on the 23rd of May. He is very good and the stable has in general been in better form lately - we had a horse placed today and a 24-length winner at Ayr the other day.
"Saturday's race looks very good and we will never beat the horse of Harry Fry's (Unowhatimeanharry) but we are not greedy and hopefully he can make the first six.
"He likes the uphill finish at Cheltenham, especially when he has his ground, and has had success there over the years.
"It was a nice run at Carlisle last month, when he was giving the winner 13lb and the second 14lb. It was his usual performance and though time tells us he should be becoming a decrepit old racehorse now, he shows no signs of it at all.
"His Carlisle run qualified him for the Pertemps Final at The Festival. I wouldn't rule anything out, but we will take it one race at a time with him."
Unowhatimeanharry (Harry Fry) heads the entries for the galliardhomes.com Cleeve Hurdle. The nine-year-old has racked up eight consecutive wins for trainer Harry Fry including victories in the Albert Bartlett Novices' Hurdle at The Festival in March and the G1 JLT Long Walk Hurdle at Ascot on his latest outing in December. He is the current 5/2 favourite with the sponsor for the Sun Bets Stayers' Hurdle at The Festival.
Other leading entries include Ballyoptic (Nigel Twiston-Davies), who fell at the final flight in the JLT Long Walk Hurdle, plus Un Temps Pour Tout (David Pipe) and Ptit Zig (Paul Nicholls), who were third and fourth in the same race.
The 2015 Stayers' Hurdle winner Cole Harden (Warren Greatrex) and Kotkikova (Nicky Henderson), a prolific winner in France, have also been engaged.
A fantastic nine-race card on Festival Trials Day also features the £100,000 G2 BetBright Trial Cotswold Chase (2.15pm, 3m 1½f, 11 entries), in which Timico Cheltenham Gold Cup favourite Thistlecrack (Colin Tizzard) is set to clash with popular chasers Smad Place (Alan King) and Many Clouds (Oliver Sherwood), the last two winners of the race.
Irish raider Un De Sceaux (Willie Mullins) heads seven entries for rearranged £70,000 Grade One Spectra - Cyber Security Solutions Clarence House Chase (1.45pm). The two-mile contest has been rescheduled following the abandonment of Ascot on Saturday, January 21.
Another added bonus to the race programme is the £25,000 Glenfarclas Cross Country Handicap Chase (2.50pm, 3m 6f 37y, 15 entries), which was rescheduled following its abandonment at The Open in November.
Racing starts at noon with the £30,000 G2 JCB Triumph Hurdle Trial (2m179y, 11 entries) and concludes with the £25,000 Steel Plate And Sections Handicap Hurdle (4.35pm, 2m 1f).
The gates open at 10am and there is FREE entry for accompanied children aged under 18.
The going at Cheltenham is currently:
Chase and Hurdle Courses: Good to Soft
Cross Country Course: Good, Good to Soft in places
GoingStick readings at 2.00pm today: Chase/Hurdle 6.6, Cross Country 7.3
Conditions are forecast to be dry and cold until Friday. Milder conditions are then predicted, with some rain on Friday/Saturday yielding between three and five millimetres.
Frost covers were put down this morning on the Chase & Hurdle Course ahead of a possible fall in temperatures on Thursday night. Vulnerable parts of the Cross Country Course have also been covered.