Thomson holds a useful eight-point advantage over Pippa Nolan on Cartoon II as they go into today's cross-country phase, with fingers crossed that a promising weather forecast will prove accurate.
Few have forgotten the torrential rain of the last two cross-country days at Blenheim.
'If it rains any more, the ground will be very holding,' Thomson said. She may opt for some of the slower and safer routes today, having had a run-out at Gatcombe last month with King Samuel who tends to get anxious over demanding courses. For that reason, Thomson will not consider running the horse at Badminton next year. 'It would be mean to ask him,' she said, 'he's great fun as long as I don't get too ambitious.'
Next month Thomson will be driving her horsebox in a convoy of vehicles to Romania, on a third trip organised by Lucinda Green in order to deliver supplies to three orphanages.
Nolan, who took over the national title from Thomson at Gatcombe last month, had problems here last year with Cartoon before she retired him. 'He'd given himself a fright at water before we came here last time, but I have much more confidence in him now,' Nolan said after moving into second place. Rodney Powell, the 1990 Badminton winner, is now lying third on Limmy's Comet with New Zealand's world champion, Blyth Tait, close behind on Ricochet. Tina Sederholm, who led on Thursday night, is fourth on Chinook II.
Owen Moore, the British Olympic reserve, will be first to tackle the 29 cross-country fences today on King's Revenge who is now 28th.
BLENHEIM AUDI HORSE TRIALS: Standings after dressage: 1 King Samuel (M Thomson, GB) 39.8pens; 2 Cartoon II (P Nolan, GB) 48.6; 3 Limmy's Comet (R Powell, GB) 49.2; 4 Ricochet (B Tait, NZ) 50.6; 5 Chinook II (T Sederholm, GB) 51.2; 6 Carmody Street (F Cribb, Aus) 51.4.