More stringent load tests on rear wings were implemented after qualifying at the Qatar Grand Prix in response to Red Bull’s recent complaints about Mercedes amid suspicions relating to the legality of its F1 rival’s rear wing. 

Red Bull has been applying pressure on the FIA over what it believes to be possible illegal rear wing activity on the Mercedes that has given it a top speed edge in recent races. 

During the Qatar weekend, Horner said Mercedes straight-line speed was now back to a normal level, with F1’s leading two teams almost equal in terms of top speed at Losail. 

"I think what we’ve seen in recent races has been an abnormal straight-line speed,” Horner said after the race in Qatar. 

“The fact that Toto [Wolff] has been at pains to point out that there have been gains in our straight-line speed when nothing’s changed.

“I think it is encouraging that for the first race since prior to Silverstone, we’ve been able to match them in straight-line speed and it’s been exponential increase in races.”

The new FIA tests that will continue to be conducted over the remaining two rounds in Saudi Arabia and Qatar, though any teams found not to have met the standards of the flexibility test will not be at risk of exclusion. 

Mercedes’ wings have passed all of the current inspections but Horner is pleased to see additional monitoring come into effect. 

"I think that it’s being well policed," he added. “And I’m confident that the tests that have been introduced should eradicate any ability to circumnavigate.”

In a reference to Red Bull's 'score mark' photograph claims, Mercedes team boss Toto Wolff quipped: “Have they shown some data or photographs about the straight-line performance?

"It's a track here that is less power-sensitive and I think they've just done a good job. Their straight-line speed with the big wing is identical to ours. So I'm happy that they are happy.

"Let's go to Saudi Arabia and maybe we'll hear some comments again. In a way, the debates that are being kicked off and launched, I cannot follow any more.

"We're struggling to keep up with comments on the rumours that are being made from that side."