Alessia Russo scored the only goal to earn England a 1-0 victory in Iceland on Saturday and a fourth win in as many 2027 Women's World Cup qualifying games.
The Arsenal striker picked out the far corner with a precise low shot midway through the first half in Reykjavik after an excellent burst from Lauren Hemp, who supplied the pass for Russo.
The Lionesses were also indebted to goalkeeper Hannah Hampton for three crucial saves in the second half, which preserved England's 100 per cent record and kept them three points clear of Spain.
Two-time European champions England moved above Spain in Group A3 earlier in the week after beating the World Cup holders 1-0 at Wembley. Only the top team progresses automatically to the tournament in Brazil next year.
"The most important thing is that we have played four and have 12 points. No game is easy, we don't take anything for granted and we're in a really good position," England boss Sarina Wiegman told ITV.
"We know how good Spain are, and Ukraine too.
"I am happy with six points (from this week's two fixtures). The players go back to very important games with their clubs and then we go again in June."
Edna Imade netted two headers as Spain crushed Ukraine 5-0 in Cordoba.
Spain roared into an immediate lead through Bayern Munich striker Imade. She powered home a fine header from Lucia Corrales's cross before 90 seconds had passed.
Spain were without injured three-time Ballon d'Or winner Aitana Bonmati, but her Barcelona teammate Alexia Putellas ran the show from midfield.
The visitors almost levelled before the break when Olha Ovdiychuk fired against the post.
Spain's second goal was a carbon copy of the first, with Corrales crossing from the left and Imade nodding home just over a minute into the second half.
Salma Paralluelo hit the post before Maria Mendez headed home the third from Barcelona teenager Vicky Lopez's cross.
Eva Navarro notched Spain's fourth with a deflected effort from the edge of the area and Lopez showed neat footwork before tapping home the fifth.
"I think we could have scored even more goals... coaches always want to improve," said coach Sonia Bermudez.
"The plan was to use the flanks and with Edna, she's got the power that allows her to do damage."
Spain host England in Mallorca on June 5, a game they likely have to win if they want to qualify directly and avoid the play-offs.
"Now we'll take a breath and then start thinking about England," added Bermudez.
Germany dropped their first points in Group A4 after drawing 0-0 away to neighbours Austria. Norway are just a point behind after Signe Gaupset grabbed a stoppage-time winner in a 3-2 victory in Slovenia.
Leaders Denmark were held 0-0 at home by Italy in Group A1, which allowed Sweden to close to within a point after a 1-0 win over Serbia.