Firstly, we don't want her to sing: they put that voice through electronic devices so it sounds like a robotic answering machine for a reason, you know.

Secondly, Spears puts on a big-top pop show. And doesn't pretend otherwise.

Like three tenors singing in a football stadium, big pop shows aren't really about the music.

From Madonna and Janet Jackson to Christina Aguilera, Kylie and Ricky Martin - did you really think they all sang every note live? These shows are about the flash of the costumes, the flair of the dancing, the wow of the special effects and the eye-popping gimmicks enjoyed in the company of thousands of like-minded screaming souls.

So forget ''authenticity''. The question is whether Spears delivers a good pop show.

Three stages set in the round, circus and bondage gear, gymnasts and wrestlers, legs akimbo and pole dancing and three costume changes - that's just the first four songs.

Soon there is lingerie, dry humping and dragster bikes.

Nothing is static for more than seconds and with the badly overblown sound you can be distracted from the poor material and the fact La Britney doesn't dance so much as move a lot.

She may save her best songs, Toxic and Slave 4 U, not to mention the compulsive Womaniser for the end, but by then the selling has been done.

Empty and trashy it may be but this is pop spectacle done with shameless gusto.

Just like it says on the packet.