HAMPSHIRE twin sisters Catherine and Lizzy Ward Thomas have been doing cartwheels ever since their album of that name entered the charts at number one last September.

"It still sounds very strange: a number one album!" says 23-year-old Catherine, as Ward Thomas set out on a 22-date spring tour with three Yorkshire gigs on successive nights, starting at York Barbican on Tuesday, after selling 75,000 copies of Cartwheels.

"It was such a crazy, full-on year for us in 2016; we did so much, and now we want to make our set list a bit different from last year. We definitely want to put a new song in there, and that's why we had a whole load of writing sessions booked for February and March. We had some new songs we wanted to work on and we had a few songs that didn't make it on to Cartwheels that we wanted to record."

Ward Thomas went into the sessions loaded with ideas. "We have some very exciting go-to writers that we work with, like a writer coming over from Los Angeles," says Catherine. "We call ourselves The Dream Team: Catherine, Lizzy...Jessica Sharman, from London, Rebekah Shreck, from Los Angeles.

"We've also arranged some sessions with some writers who are really current. We've always said that when we go into writing sessions, we leave out egos at the door, blurt out our ideas, and if something comes out of it, great.

"We like writing with other people, Lizzy and I will come up with a concept, and someone else will come up with something to add to that concept, drawing on their own experiences."

Ward Thomas made their mark initially with the country harmonies of 2014's From Where We Stand but have since expanded their repertoire. "We've always loved the country style, but by the time we started writing the second album, we felt we'd done it for a while; we'd lived in Nashville, and we now felt we wanted to write songs inspired by country, but if the song felt more poppy, we'd take it that way," says Catherine. "We all feel we want to experiment and try things, but we'll probably end up back where we started on the next album!"

Ward Thomas have been showing off their increasing diversity in their choice of singles off Cartwheels, following up Boomerang with Material this month. "Me and Lizzy made the decision when we first embarked on this career that we wanted to be album artists, but there are 14 songs on the album and we want to show off our different aspects with our singles," says Catherine. "Lizzy always said that an album is a portfolio of what you're going through at that time, and now I'm getting to quote her saying that!"

Ward Thomas, incidentally, have filmed an interactive video for Material that allows the viewer to flick between Catherine and Lizzy’s vocals, either solo or together in harmony, while also gaining an insight into the twins’ different personalities. In harmony, the sisters' performances are shown side by side, and when isolated, viewers can watch either Catherine or Lizzy interact with various props and the sets around them.

In between the singles came a March EP of cover versions, A Shorter Story, that showcased Ward Thomas putting their stamp on The Blower's Daughter, What Goes Around...Comes Around, Shine, Walls and Better Be Home Soon. "We've been playing around with cover versions as part of our acoustic Snug Sessions videos for a few years now and mostly they've gone down really well," says Catherine. "We recorded the EP over two days and have tried to bring something new and different to each song while at the same time respecting the original versions. Hopefully people like them."

Ward Thomas's busy diary for 2017 shows no sign of slowing down: they have been added to the bill for Tom Petty's Hyde Park show on July 9; festival appearances are confirmed at Latitude, Isle of Wight, Cornbury and Harvest, and in August they will support one of their all-time heroines, country musician Miranda Lambert, on her British tour A return to Yorkshire is on the way too: Catherine and Lizzy are to play Pocklington Arts Centre's Platform Festival at The Old Station, Pocklington, on July 15, as part of a Saturday line-up with KT Tunstall, Newton Faulkner, York singer-songwriter Benjamin Francis Leftwich and rising Yorkshire country singer Holly Macve.

Bring on the cartwheels.

Ward Thomas play York Barbican on May 2; The Plug, Sheffield, May 3, and Church, Leeds, May 4. Tickets for their 7.30pm York concert are on sale on 0844 854 2757.