Problem with wife or series IIa?

Could anybody help provide an explanation for a problem experienced by my wife while driving our Series IIa today.

Now my wife is not renowned for her ability of describing fault conditions with vehicles but here goes.....

"Having driven around town for 5 or 10 mins I parked and went shopping. When I drove away after a while it was struggling to go up hill. I had to change down when normally I wouldn't. The engine seemed OK but it was like something was pulling the car back. It just wasn't right! I tried pulling and pushing those funny red and yellow knob thingies - you know the ones joined to that gearbox thingy but then it went very very slowly and the engine made a lot of noise so I parked and walked"

My first thought was that the brakes were binding but having driven the car for 30 mins with plenty of hard braking I can't find fault. Everything seems fine and its driving as well as ever.

Now she got a little upset the second time I asked if the Handbrake was applied, and hit the roof when I suggested it may have been the fact she was more used to driving a modern vehicle.

I am wondering if it this could be caused by transmission wind-up. The kids were larking about in the car before she left and it is possible they could have selected four wheel drive!

Any thought on whether this could be an explanation?

Many Thanks

David.