Disclaimer: I am writing this at midnight after a day of rehearsal that finished at 11pm. Please forgive any errors of grammar or punctuation – I am very tired.

Tomorrow night at 7.30pm I will be making my debut in the West End, performing in Eyebrow Productions’s The Boy Friend, a musical that is being rehearsed in just 48 hours and put on to raise money for the Prince’s Foundation for Children and the Arts.

The last time I was on stage was in a restoration comedy at university. My part in it was so small that I can’t even remember the name of the play. The last time I did any singing on stage was in a mock oratorio about Admiral Nelson called Hip-Hip-Horatio at the age of 11. The last time I did any dancing on stage was in a ballet recital at the New Player’s Theatre at some point in my early teens. It went so badly that I have never watched the video of the performance.

My role in The Boy Friend, fortunately, is a very small one: I am in the chorus, playing a waitress in the party scene. Even so, there is plenty to do. Now, I’m no singer, but the singing I can pretty much manage; it’s actually quite fun. It’s the dancing that’s causing me trouble. People keep saying that it will be fine, but I’ve seen no evidence of that so far. Last thing this evening we did the dress rehearsal (well, run through with costumes and orchestra in the rehearsal room – Her Majesty’s Theatre wasn’t available tonight – I can’t think why) and I got about 8% of the steps right. Anyone who’s coming to see the show tomorrow evening, please judge me kindly.

The good news is that while my performance is likely to be risible, the rest of the cast will be doing a fantastic job. The Boy Friend is not a very long show, nor a very complex one plot-wise, but it’s full of huge dance numbers and tricky harmonies, making putting on the show on in just a weekend quite a challenge.

I was ready to believe in the professionalism of my fellow performers when I first glimpsed them all swanning around in dance wear at the start of the rehearsal process last night, but what they’ve achieved in the last 14 hours is nothing short of astounding. I know they’re trained and everything, but I still can’t understand how they’ve mastered so much in such a short time and, crucially, been able to remember it all under such intense pressure. The dress rehearsal tonight wasn't quite as flawless as you’d want an actual dress rehearsal in a conventional show to be, but it was pretty damn good. We’ve got work tidying up to do tomorrow, of course, but on many occasions I was amazed by what I saw tonight.

I've also been really impressed by the incredibly smooth running of this barmy operation. As director John Sheerman blocked the show chronologically in one room, dance numbers, songs and other bits and bobs were rehearsed elsewhere, with performers streaming in and out of different rehearsal spaces throughout the day. The creative and production teams are enormous, with associate and assistant directors and choreographers dealing with particular parts of the show to make sure that everything is ready in the limited time available. Wardrobe was on site too today - I was fitted for my costume in the afternoon and by the time of the dress rehearsal it (along with the other 100-plus costumes in the show) had been taken in, added to and adapted to turn me into a 1920s waitress. Impressive stuff.

There are lots of other people I should mention but it's time for me to sign off now and get some rest (one quick big up to my buddies in the party ensemble, who have all been immensely helpful, patient and understanding) – tomorrow is another very long day. I'll try and blog again at some stage if I get a free moment. If you haven't already got your tickets to the show, you can book them here. It's all for a very good cause, and as well as seeing a fantastic show, you'll be able to have a little chuckle at me attempting to sing and dance.