Rusedski needs to win his semi-final against Sweden's Thomas Johansson at the Stockholm Open today to ensure that Britain provide two of the elite field for the first time since the year-end finale, formerly the Masters, began in 1970.
Henman is the first English-born player to qualify, his achievement coming after the Canadian-born Rusedski's breakthrough for his adoptive Britain in Hanover last year.
Since Rusedski decided to play under the Union Jack in 1995, he has set a pattern of success which Henman has closely followed. A year ago, Rusedski became the first British player to crack the top 10 in the ATP Tour's world rankings. Henman became a top 10 player in August.
Henman defeated Sweden's Magnus Gustafsson in a tense quarter-final at the Stockholm Open last night, 6-3, 3-6, 7-6. Rusedski earlier advanced to last four with a 7-6, 1-6, 6-3 win against the Canadian Daniel Nestor.
Kafelnikov stayed in the race for Hanover with a 6-1, 6-1 win against Guillaume Raoux, of France, to reach the semi-finals of Kremlin Cup in Moscow. Kafelnikov plays the Swiss Marc Rosset today.
Henman took a day-trip to Hanover by private aircraft last year to play a match as a substitute. He won $110,000 (pounds 67,500) for defeating Kafelnikov in the last round-robin contest and then returned to Telford, where he completed a hat-trick of singles titles at the Guardian Direct National Championships.
Although he enjoyed the experience, Henman said he felt he had "gate- crashed" the Hanover party. The Spanish player Felix Mantilla agreed with Henman's description. He thought he should have had the invitation.
Rusedski had already been afflicted by injury when Sergi Bruguera had to retire with a back problem after playing two of his three matches. Time was running short, and the choice of substitutes was limited.
Thomas Muster (No 9) had already earned the $40,000 (pounds 25,000) alternate's fee by stepping in for Rusedski against Carlos Moya. Marcelo Rios (No 10) was at home in Santiago, Chile, Richard Krajicek (No 11) was injured, Alex Corretja (No 12) was ineligible under the ATP Tour's rules because he was already playing doubles at a Challenger event in Andorra. Petr Korda (No 13) was having a nose operation. Gustavo Kuerten (No 14) was in Brazil. Goran Ivanisevic (No 15) was injured.
When it came to No 16, the ATP Tour said, Mantilla's telephone rang and rang without response. After the midnight deadline (local time) was passed, the call went out to Henman (No 17).
The 24-year-old from Oxford made sure he makes the trip on merit this time.
Henman began smoothly against Gustafsson, breaking the Swede for a 2- 0 lead in the opening set and cruising to the first set 6-3. The second set, however, produced a few wobbles for the British third seed, who dropped serve for 0-2, broke back but lost his serve again to trail 2-4. Gustafsson levelled the match two games later.
Henman led 4-2 in the final set but the Swede broke back and forced a tie-break, but Henman swept through that 7-0.