Cambridge Grammar of English Hardback with cd-rom a comprehensive Guide

The present progressive for narrative build-up 

360b

When a story builds towards a peak or climax, especially in spoken story-telling,

the verb form may change to the present progressive to describe the background

to the main event(s) or to dramatise an ongoing event:

And he walked right up in the pitch blackness, on the top edge of this crane.

We’re all sitting there, and the police turned up, and he said, ‘What’s going on,

boys?’

I said, ‘There’s been a pigeon in here eating my sandwiches and I had to throw

a few things at it’. She used to have the windows wide open, you know, winter,

summer, everything. So, anyway,

I’m telling her off for all this mess on the floor,

I went to pick the tail up, some of the bits the other side of the bed, and as I got

up

I’m looking straight into this pigeon’s eyes.