England won their first men's World Cup at Lord's this month but were bowled out for 85 against Ireland on their return to Test cricket.

The hosts ultimately won by 143 runs but Giles said he hoped the Test had "given us a bit of a jolt".

"Against any Australian team in any form, you've got to raise your game," the former England spinner said.

Australia hold the Ashes after their 4-0 victory down under in 2018-19, but England have not lost a series on home soil since 2001.

"We've had some criticism that we shouldn't have played any of the guys who played in the World Cup final [against Ireland] but I look at it the other way - it was an opportunity for them to perhaps be shocked back into Test cricket," Giles told BBC Sport.

"There was undoubtedly a hangover, a little bit, from that World Cup win - the guys were mentally and physically tired.

"It's always concerning when you get bowled out cheaply. When you get out there, a lot of it will come down to your mental approach."

The first Test of the five-match Ashes series begins on Thursday at Edgbaston.

'Tough cricket played in right way'

James Anderson is expected to be fit for England's Ashes opener on Thursday

England's leading Test wicket-taker James Anderson, who missed the Ireland Test with a calf injury, was one of three players who took part in an optional training session on Monday.

Anderson is expected to be fit for the Ashes opener, while England will make a decision on Jofra Archer, who has just returned from a side strain.

Fast bowler Stuart Broad and batsman Jos Buttler were the other two players who took part in the session.

England have struggled to find a consistent top-order partnership since Andrew Strauss retired in 2012, although captain Joe Root has said he has "no concerns" about his side's batting.

Australia have also struggled in English conditions - their recent warm-up match saw 32 wickets fall in two days - and Giles said the series was a big opportunity for batsmen on both sides.

"There's been a lot said about both bowling attacks but maybe a couple of batters will surprise people in this series," he said.

"When you get out there on Thursday, a lot of it will come down to your mental approach. I know from experience it does wear you mentally and physically.

"You always want to play against an Australian team that plays this game hard and tough - that's my experience of playing against Australia.

"It's tough competition; there's a lot riding on this series. Expect it to be played tough, but it's got to be played in the right way."

Former batsman Steve Waugh, who was captain when Australia last won the Ashes in England, said there will not be "any shrinking violets out there".

"We are brought up to play in a positive, aggressive manner and I don't see that being any different," said Waugh, who is a mentor to the current Australia side.

"This side is going to be combative because that is the Australian way - but they know they can't cross over the line."

What is the World Test Championship?

Players will have their names on the back of their whites for the first time during the Test Championship

The new World Test Championship begins with the first Ashes Test on Thursday.

The top nine Test teams in the world are involved in the tournament, which sees 72 matches contested between August 2019 and June 2021.

Each nation will play six series in the two-year period, three home and three away. Each series counts for 120 points.

Points are on offer for every match in a series - meaning teams can still win points even after a series has been decided, giving teams more to play for in otherwise dead rubbers.

In June 2021, the top two teams will then compete in the ICC World Test Championship final, which will be held in England.

"Test cricket around the world has probably become a little bit marginalised," Giles said.

"Anything we can do to protect Test cricket, which is very important for us and should be for world cricket, is a great thing."