1978: three-year-old season

Thatching sustained a broken bone in one of his hind feet and did not race until the autumn of his three-year-old season. In October 1978 he was sent to England to make his racecourse debut in the Severals Stakes over one mile at Newmarket Racecourse. He started the odds-on favourite but finished second, beaten three lengths by the Guy Harwood trained Portese. Later in the month he ran twice at Leopardstown Racecourse, finishing second over seven furlongs and then recording his first success in a nine furlong maiden race.^[3]

1979: four-year-old season

Thatching began his four-year-old season in the Group Three Earl of Sefton Stakes over nine furlongs at Newmarket in which he finished fifth behind his owner's more fancied runner Hawaiian Sound. After being exposed as some way behind the best at longer distances, Thatching was then campaigned over sprint distances and showed much improved form. In May he contested the Group Three over six furlongs at York Racecourse and started at odds of 17/2.^[4] Owing to a strike by employees of Racecourse Technical Services the starting stalls were not available and the race had to be started by flag. Thatching was left behind at the start but recovered to take the lead inside the final furlong, and despite veering to the left in the closing stages he won decisively from Persepolis and the Ayr Gold Cup winner Vaigly Great. Later in the month, Thatching started favourite for the Temple Stakes over five furlongs at Sandown Park Racecourse but finished fifth behind Double Form after hanging badly again in the final quarter mile. O'Brien was extremely disappointed with the performance, as the colt had been performing impressively in training.^[5]

For his next race, the Group Three Cork and Orrery Stakes at Royal Ascot in June, Thatching was equipped with blinkers for the first time. Starting at odds of 6/1^[4] in a field of seventeen runners, the colt demonstrated what Timeform described as "remarkable power", racing among the leaders from the start and drawing clear in the closing stages to win by four lengths from the filly Rose Above. Thatching was then moved up to Group One class for the July Cup at Newmarket in which he started 2/1^[4] favourite against a strong field including One In A Million, Vaigly Great, Sigy (Prix de l'Abbaye), Devon Ditty (Cheveley Park Stakes), Absalom (Vernons Sprint Cup). Piggott sent Thatching into the lead shortly after the start and by half way most of the other runners were struggling to match his pace. In the last quarter mile he pulled clear of the field to win by five lengths from Vaigly Great. Later in the month, Thatching was moved up in distance for the Sussex Stakes over one mile at Goodwood Racecourse but failed to stay and finished unplaced behind Kris. The colt then returned to sprinting for the William Hill Sprint Championship over five furlongs at York. He took the lead just after half way but veered to the left, causing interference to several other runners before crossing the line two and a half lengths clear of Ahonoora with Abdu third and Double Form in fourth. Following an inquiry by the racecourse stewards, however, Thatching was disqualified and relegated to last place, whilst Piggott received a four-day suspension for his ride.^[5]

Thatching's last was the Prix de l'Abbaye over 1000 metres at Longchamp Racecourse in October. Drawn on the outside of the thirteen runner field he was never able to get into contention and finished unplaced behind Double Form.^[5]