She plays Monica, acerbic secretary to actor, charmer and diva Garry Essendine, played by Mr Selfridge star Samuel West.
She said: “It is one of his best shows and I think having not done stage work for so long, I simply wanted to go out there and prove to myself that I could do it.
“It is nice to do comedy, it is all written well and constructed well.”
By the verynature of the source material, it is an exaggerated piece and Phyllis is relishing the chance to do something.
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She said: “It is a big, blowsy over-the-top piece and it is nice to play that rather than containing it.
“That will be the nice thing about coming to Milton Keynes Theatre - it is a really big venue and the show really fills it rather than trying to be intimate.
“The audiences have really appreciated what we have been doing so far and we hope that continues throughout the rest of the tour.”
Among a smattering of television appearances, she will be best known for her roles in the drama series Lovejoy and the Sunday night smash hit Downton Abbey.
Phyllis said: “Many actors will always get one part in their career which is joyous and something they are recognised for the public.
“I’m very lucky to have had two.
“Doing Lovejoy was such good fun, every single moment and working with brilliant people like Ian McShane, Dudley Sutton, Chris Jury and Malcolm Tierney who is sadly no longer with us. We all laughed a lot.”
She is also looks back on sadness that Downton Abbey had to end and there was a lot of emotion filming the final series.
Phyllis said: “I think we all knew it was going to end, but it was such a great job to work on a show by Oscar-nominated Julian Fellowes.
“We were a real gang and got to know not just the fellow actors but also the crew who were with us throughout the run. We filmed at a country house and the final scenes we did there, we found it emotional knowing it would be the final time we would shoot there. There were lots of moments like that.”
Present Laughter comes to Milton Keynes Theatre from Monday July 11 to Saturday, July 16.
Tickets cost from £15 and are available from the box office on 0844 871 7652.
Or they can be bought online by visiting www.atgtickets.com/miltonkeynes.