Peaty missed the World Championships last month with a fractured foot but returned to win 50 metres breaststroke gold at Birmingham 2022.

The enforced absence of Russia’s European record-holder Anton Chupkov, champion in the 200m breaststroke in 2018 and 2020, mean that there will definitely be new European champions in men's breaststroke.

Peaty won 50m and 100m titles at the last European Championships in Budapest last year.

Arno Kamminga of The Netherlands, who won a 100m breaststroke Olympic silver medal in Tokyo, and Italy’s Nicolo Martinenghi, the bronze medallist, will be hoping to take advantage of Peaty's absence at Foro Italico.

Hungary's Olympic 200m butterfly champion Kristóf Milák, who completed the 100m and 200m butterfly double in home waters at this year's World Championships, is expected to also compete in the freestyle at the Europeans.

Romania's David Popovici, who won the world freestyle sprint double in Budapest in June and July, also seems likely to be a big attraction in Rome.

Popovici certainly knows the Rome pool well as he swam to three gold medals and a junior world record in the 100m freestyle at last year's European Junior Championships there.

Racing begins tomorrow with the heats of the 50m men’s butterfly.

Hungary’s triple Olympic gold medallist Katinka Hosszú, who won world 400m individual medley gold in this very pool, has targeted her 100th international gold medal.

Sweden’s Sarah Sjöström returns to the pool where she first won world gold in 2009.

Since winning 50m freestyle and butterfly gold in Budapest, she tested positive for COVID-19, but is expected to compete in the same events in Rome and has a surprise in store when she removes her swimming cap to reveal purple hair.

"I like to surprise people when I take my swimming cap off, so many Swedish girls have blonde hair so I like to surprise people," Sjöström said.

The first medals are due to be won in in artistic swimming, where great things are expected of Ukraine’s Marta Fiedina, who won four European golds last year.

Some 557 competitors from 46 nations are expected to take part in the European Aquatics Championships.

The host nation Italy is set to field the largest team which is likely to be around 58.

The European Aquatics Championships are not a part of the multi-sport European Championships, due to take place over the same dates in Munich.