We are very pleased to be able to report an operating profit driven by year-on-year gross margin growth and year-on-year revenue growth for the last 6 months despite challenging market conditions.
Our early decision to stay true to our values and prioritise our team and partners by avoiding any furlough or COVID related cuts, evolved during the period and we invested further in growing our teams, all of which has proven fruitful. Revenues increased 13% in the first half from £26.3 million to £29.6 million for the comparative period last year. More significantly, this revenue growth was combined with a significant increase in Gross Margin from 8.8% to 12.8%; the cumulative effect of both was to increase Gross Profit by £1.5m from £2.3 million to £3.8 million, an increase of 65%. The improvement in Gross Margin resulted from our evolving product mix towards higher margin, more technical products through Northamber and AVM.
Previously discussed lockdown challenges have impacted performance in some of our strategic business units and our subsidiary AVM, as site restrictions limited access for higher end projects but we are hopeful of improved performance as these restrictions ease later in 2021 and beyond.
It is clearly pleasing to see a 65% increase in Gross Profit year on year however our focus on efficiency and cost management remains strong; we remain focused on optimising the business for long term results and investing as needed to drive this. Our warehouse changes in the last financial year was a significant undertaking and we are seeing the benefits through an improved cost base, whilst still providing significant capacity to scale the business further.
To support this increase in Gross Profit, and in anticipation of continued growth, our Distribution costs increased year on year from £1.53 million to £2.28 million; part of this costs increase also came from the addition of AVM to the group. Administrative costs also increased marginally from £1.15 million to £1.29 million as we continue to invest to support our future plans.
Stock levels are higher than last year at £8.4 million against £4.5 million, in part due to the AVM acquisition, and also as we continued to seek to profitably support our partners by maintaining sufficient stock in country during the uncertainty of logistics derived from Brexit and COVID impacts on supply chains. We see our flexibility on local stock levels as a key driver of our future with our partners, who have recognised the benefits of Northamber's financial strength in underpinning this.
Cash was £10.8 million at 31 December 2020 compared with £14.7 million at 31 December 2019, reflecting the sale of the Brooklands distribution centre and the purchase of the new Swindon warehouse, the acquisition of AVM and a new office, where AVM is now located. With Fixed Assets at book value at £7.1 million, including three unencumbered freehold properties, the Group's overall financial position is very sound.
Net Assets at 92.3p per share are considerably in excess of the average price of the ordinary shares throughout the period.
As in previous years, your Board has had regard to the strength of our debt free, tangible asset strong balance sheet and is proposing the interim dividend be 0.3p, at a total cost of £81,695. The dividend will be paid on 27 May 2021 to shareholders on the register as at 30 April 2021.
The Board remain grateful and pleased for how our team continues to pull together to flexibly support our partners and each other through these unprecedented times. We strongly believe that our staff are a key differentiator for our business and we are delighted to be able to continue to grow with them and offer them continued job security. We intend to continue to invest in our evolving business model by continuing to invest in building out the best team in the market to achieve our business evolution.
In keeping with the outlook we shared in our recently published full year results, we remain cautiously optimistic that the investments we have made in supporting our partners coupled with removing the one off costs tied to moving warehouse should be reflected in the trading results for the current financial year and allow us to build on our profitable first half. We necessarily remain cautious due to the economic uncertainty, Brexit and the potential further impact of COVID on demand and the supply chain, but feel strongly that our continued focus on strategic higher margin value categories provides a solid road map for the future with profitable growth opportunities and the ability to unlock long term value for shareholders.
The strength of our balance sheet allows us to continue to do what is best for the business strategically and we continue to review organic and non-organic opportunities for growth which meet our strict criteria and add value for our shareholders.