The trouble, which forced him to retire hurt before lunch on the first day before returning to put on 205 with Mark Ramprakash, was described at first as being nothing worse than muscular spasms, but after a recurrence of pain after the first one-day international at Kensington Oval on Sunday, it turns out that the problem is disc related.
After ruling him out of yesterday's second international in Barbados, England's physiotherapist, Wayne Morton, decided on Tuesday that Thorpe would be far wiser to return home for treatment immediately.
The alternative, to move on to St Vincent and Trinidad with little chance of playing in the last three matches of England's tour, made little sense.
Thorpe said before leaving Bridgetown that he was disappointed to end his tour in this way, but was confident of playing a full part for England this summer.
He has proved a durable cricketer, both mentally and physically, since establishing his place irrefutably against South Africa four years ago, and his resolute batting on the improved pitches, which finally gave batsmen a better than even chance in the last two Tests of the Caribbean series, maintained his Test average of 40-plus.
Thorpe has more than a month to get himself fit for the first international against South Africa in May but in his absence he may be in some danger of losing his limited overs place, even though he is a good one-day player.
It is getting harder for anyone to hold a regular place in both England teams.